* gcc.c (init_gcc_specs): New function.  Make -shared-libgcc
	the default when building a shared object.
	(init_spec): Use it.
	* testsuite/lib/g++.exp: Include the directory where libgcc
	is located to the LD_LIBRARY_PATH list.
	* inovke.texi (-shared-libgcc): Document the cases in which

	* Make-lang.in (g++spec.o): Add DRIVER_DEFINES to the list
	of macros used when compiling g++spec.c.
	* g++spec.c (lang_specific_driver): Link with the shared
	libgcc by default.

From-SVN: r39408