Add GError arguments to e_phone_number_get_default_region() and
e_phone_number_get_country_code_for_region() to properly report
missing phone number: Warnings cannot be handled programatically
and make GTest based unit tests failed.

Ensure that libebook-contacts always gets linked using the C linker,
instead of the C++ automake would prefer, because of the optional
e-phone-number-private.cpp file. Without this change linking with
explicitly disabled phone number support (--without-phonenumber)
would fail because no C++ linker is know. Similarly the library
would depend on the C++ standard library if phone number was
disabled automatically, because libphonenumber was not found.

Signed-off-by: Gheyret Kenji <gheyret@gmail.com>

This is needed to properly reopen addressbooks without
specifying the full custom summary a second time.

This avoids errors of the kind "e-book-backend-file.c:1478: Failed to open
sqlitedb: table folder_id has no column named file_as" when opening an
addressbook with customized summary a second time, but with default
settings.

The sqlitedb backend and e_phone_number_compare() showed different
behavior for a few cases of national and short number matching.
This syncs the behavior.