re PR libffi/70024 (libffi ABI change w/o SONAME bump)

PR libffi/70024

  * Makefile.am (libffi_version_script): New.
  (libffi_version_dep): New.
  (libffi_version_info): New.
  (libffi_la_LDFLAGS): Include libffi_version_info, libffi_version_script.
  (libffi_la_DEPENDENCIES): Include libffi_version_dep.
  * acinclude.m4 (LIBAT_ENABLE, LIBAT_CHECK_LINKER_FEATURES): New.
  (LIBAT_ENABLE_SYMVERS, LIBAT_BUILD_VERSIONED_SHLIB): New.
  (LIBAT_BUILD_VERSIONED_SHLIB_GNU): New.
  (LIBAT_BUILD_VERSIONED_SHLIB_SUN): New.
  * configure.ac: Invoke LIBAT_ENABLE_SYMVERS.
  * libffi.map: New file.
  * libtool-version: Increase to 5.0.0.
  * Makefile.in, configure: Rebuild.
  * man/Makefile.in, testsuite/Makefile.in: Rebuild.

From-SVN: r233921