configure.ac (BACKTRACESPEC): Remove definition, but continue to AC_SUBST definition from configure.host.

	* configure.ac (BACKTRACESPEC): Remove definition, but continue to
	AC_SUBST definition from configure.host.
	* configure.host: Don't use -fno-omit-frame-pointer. Set BACKTRACESPEC
	to -fomit-frame-pointer on 32-bit x86 targets.

From-SVN: r100469