configure.in: When target is sparc* and tm_file contains 64, test for 64bit support...

configure.in: When target is sparc* and tm_file contains 64, test for 64bit support in assembler.

* configure.in: When target is sparc* and tm_file contains 64,
test for 64bit support in assembler.  If not supported, remove
sparc/t-sol2-64 from target-dependent Makefile fragments.
(AS_SPARC64_FLAG): Define to the assembler flag for 64bit.
(HAVE_AS_OFFSETABLE_LO10): Rework test to use these flags.
(HAVE_AS_REGISTER_PSEUDO_OP): Use config.cache.
* acconfig.h (AS_SPARC64_FLAG): Added.
* configure, config.in: Rebuilt.
* config/sparc/sol2-sld-64.h: Same as sol2.h, if without 64bit
support.  Use AS_SPARC64_FLAG.

From-SVN: r30827