Makefile.in: Call gcc/ada/Makefile directly, not through the intermediary of gcc/Makefile.

	* Makefile.in: Call gcc/ada/Makefile directly, not through the
	intermediary of gcc/Makefile.  Incorporate all necessary parts of
	rules from gcc/ada/Make-lang.in, including extra gnatlib/gnattools
	targets, rts-zfp, rts-ravenscar.  Get needed bits of GCC
	configuration from (new) gcc/libada-mk.  Decide what gnatlib variant
	to build in configure.ac, not here.
	* configure.ac: Provide Makefile.in with the new information it needs,
	such as GCC's tmake_file and xmake_file.
	* configure: Regenerate.

From-SVN: r80711