* removing duplicate target links

* Adding dependencies at the right level

It is used in the library with #2734, and not linking with it
breaks users of the library: https://bugs.debian.org/1008817

Co-authored-by: penmetsaa <penmetsaa@google.com>

- Faced link errors stemmed from mismatch of api definitions of absl::node_hash_set. So explicitly mentioned this lib as dependency during linking. This is common case/solution for absl hash set lib's link errors as per community.
- Decided to continued to have wrapper (stringutil), so that in future it's easy if we decided to change implementation; client code is safe. Changed most of the implementations & data structures in stringutil, to use abseil stuffs more.
- Though absl::string_view is suitable for most cases where we want immutable/read-only string structures, limiting to stringutil apis, not changing public API signatures (even though no compliance issue); reason: reduce dependency on abseil libs.
- Abseil specific changes done:
    - std::set => absl::node_hash_set
    - std::map => absl::node_hash_map
    - Using absl alternatives for “SplitStringUsing” API and “StringHolder” class impl.
    - Replaced manual impl of prefix and suffix checks with absl::StartsWith() and absl::EndsWith.
    - Similarly used absl::StrReplaceAll, absl::StrCat, absl::StrAppend where possible; and for type conversion apis.
- Note: Tried applying parameter packs to replace manually written duplicate ```StrCat``` apis (for accommodating more number of parameters of same type), but it did not go well when different type arguments passed. Eg char, int types to be converted to StringHolder; faced constructor implicit conversion issues.

* fixing: if (${USE_POSIX_THREAD} ... causes a syntax error, adding
a semicolon to the flags

* Metadata updates for release 8.12.41 (#2718)

* Penmetsaa maven update release 8.12.41 (#2719)

* [maven-release-plugin] prepare release v8.12.41

* [maven-release-plugin] prepare for next development iteration

* Update README.md (#2720)

Co-authored-by: penmetsaa <penmetsaa@google.com>

@API updates:
- Migrating from associative containers to more performant types. Eg: map to absl::btree_map.
- Synchronise the write access to map "AreaCodeMaps" using absl::Mutex locking api.
- Use more of absl:strings packages like absl::StrReplaceAll

@Build updates:
- To build (CMake) against absl packages, the minimum version of compiler is CPP11+, whereas earlier we are not mandating this.
- We are upgrading CMAKE version also to automate building the external absl packages.

The change is announced. Please report issues in case of any breakages.
https://issuetracker.google.com/issues?q=componentid:192347%20555

- When building as a dependency using cmake's add_subdirectory() use the
  current source directory instead of the top level source tree.

Add ability for the C++ library to link against protobuf-lite. .

Add build option REGENERATE_METADATA   to disable regenerating the metadata.

Include modification from Dominic Battre

* Metadata updates for release 8.9.0

* release notes formatting fix

Fixes porting issue on macOS and maybe elsewhere.

* Undo reversion of RPM packaging

This reverts commit 4aaceffe5b.

* Fix CMake syntax

* Metadata updates for release 8.5.0

* Corrected release notes as US geocding update is mentioned as new addition.

* Metadata updates for release 8.2.0

* Update release_notes.txt

Sep 19, 2016: libphonenumber-7.7.0

Code changes:

Removed the dependency on protobuf (protobuf-javanano) from the Java library, resurrecting java/libphonenumber/src/com/google/i18n/phonenumbers/Phonemetadata.java which was present until libphonenumber-7.1.1.

Does not affect the C++ or JavaScript libraries.

Aug 24, 2016: libphonenumber-7.6.0
Code changes:

Refactored metadata loading and closed all streams after loading.
Made isNumberGeographical public, and changed the geocoder to use this when checking whether to give a detailed answer or country-level only.
Build changes:

Use protobuf-javanano 3.0.0-alpha-7 from Maven Central.
Metadata changes:

Updated phone metadata for region code(s): EH, ET, JM, MA, SK, SN, SY, ZM
Updated short number metadata for region code(s): ZA
Updated geocoding data for country calling code(s): 212 (en)
New carrier data for country calling code(s): 86 (zh, zh_Hant), 852 (zh, zh_Hant), 963 (en)
Updated carrier data for country calling code(s): 86 (en), 212 (en), 251 (en), 421 (en)
Deleted unsupported SingleFilePhoneNumberMetadataProto

This is similar to the fix of #822.

Also update README to cover Mac installation.

This rolls back the cmake minimum version bump in #975 since it was
backwards-incompatible, and the following #984. Not expected to cause
any new user-facing regressions, but expected to solve any that were
introduced with #975.

This is necessary to guarantee that parallel builds will succeed, all
top-level targets that include geocoding_data.cc in their builds need
explicitly listed dependencies on generate_geocoding_data to ensure that
generation of the file has finished before it is being used.

- using reserved keyword "test" in the custom target
 - bumping up the makefile version to avoid issues with policy changes
   relating to rpath

This fixes #822.

This reverts commit df876cedb5.

This commit broke internal builds with the error message:
----
CMake Error at CMakeLists.txt:422 (target_link_libraries):
  Cannot specify link libraries for target "phonenumber" which is not built
  by this project.
----

This is required with newer Boost (starting with 1.50).

R=daniel@pocock.pro
BUG=

Review URL: https://codereview.appspot.com/100910043