Remove configure tests for some linker -z options.

There are configure tests for the linker -z nodelete, -z nodlopen and
-z initfirst options.  These options were added in binutils 2.11, so
the tests are obsolete; this patch removes them.

Tested for x86_64 and x86 (testsuite, and that installed shared
libraries are unchanged by the patch).

	* configure.ac (libc_cv_z_nodelete): Remove configure test.
	(libc_cv_z_nodlopen): Likewise.
	(libc_cv_z_initfirst): Likewise.
	* configure: Regenerated.