Tests for `-ffunction-sections -fdata-sections' and sets SECTION_FLAGS
accordingly. If there is no warning when using it, take advantage of
the smaller executables that can be had with `--gc-sections'.
libphobos/ChangeLog:
* Makefile.in: Regenerate.
* configure: Regenerate.
* configure.ac: Call DRUNTIME_SECTION_FLAGS.
* libdruntime/Makefile.am: Add SECTION_FLAGS to AM_DFLAGS.
* libdruntime/Makefile.in: Regenerate.
* m4/druntime.m4 (DRUNTIME_SECTION_FLAGS): New macro.
* src/Makefile.am: Add SECTION_FLAGS to AM_DFLAGS.
* src/Makefile.in: Regenerate.
* testsuite/Makefile.in: Regenerate.