libphobos: Build all modules with -fversion=Shared when configured with --enable...

libphobos: Build all modules with -fversion=Shared when configured with --enable-shared

The libgdruntime_convenience library was built with `-fversion=Shared',
but the libphobos part wasn't when creating the static library.

As there are no issues compiling in Shared code into the static library,
to avoid mismatches the flag is now always present when --enable-shared
is turned on.  Libtool's compiler PIC D flag is now the combination of
compiler PIC and D Shared flags, and AM_DFLAGS passes `-prefer-pic' to
libtool unless --enable-shared is turned off.

libphobos/ChangeLog:

	* Makefile.in: Regenerate.
	* configure: Regenerate.
	* configure.ac: Substitute enable_shared, enable_static, and
	phobos_lt_pic_flag.
	* libdruntime/Makefile.am (AM_DFLAGS): Replace
	  phobos_compiler_pic_flag with phobos_lt_pic_flags, and
	  phobos_compiler_shared_flag.
	* libdruntime/Makefile.in: Regenerate.
	* src/Makefile.am (AM_DFLAGS): Replace phobos_compiler_pic_flag
	  with phobos_lt_pic_flag, and phobos_compiler_shared_flag.
	* src/Makefile.in: Regenerate.
	* testsuite/Makefile.in: Regenerate.
	* testsuite/libphobos.druntime_shared/druntime_shared.exp: Remove
	-fversion=Shared and -fno-moduleinfo from default extra test flags.
	* testsuite/libphobos.phobos_shared/phobos_shared.exp: Likewise.
	* testsuite/testsuite_flags.in: Add phobos_compiler_shared_flag to
	--gdcflags.