Merges upstream druntime bbfb58e8.

libphobos/ChangeLog:

2019-02-19  Johannes Pfau  <johannespfau@gmail.com>

	PR d/88127
	* m4/druntime/libraries.m4 (DRUNTIME_LIBRARIES_CLIB): Add new macro.
	* configure.ac: Use DRUNTIME_LIBRARIES_CLIB.
	* configure: Regenerate
	* Makefile.in: Regenerate
	* libdruntime/gcc/config.d.in: Add Have_Qsort_R.
	* libdruntime/Makefile.in: Regenerate.
	* src/Makefile.in: Regenerate.
	* testsuite/Makefile.in: Regenerate.

From-SVN: r268999