Add a testcase for copy reloc against protected data

Add a testcase for copy reloc against protected data

Linkers in some versions of binutils 2.25 and 2.26 don't support protected
data symbol with error messsage like:

/usr/bin/ld: copy reloc against protected `bar' is invalid
/usr/bin/ld: failed to set dynamic section sizes: Bad value

We check if linker supports copy reloc against protected data symbol to
avoid running the test if linker is broken.

Cherry-pick from master: 83569fb894050db7430047da2219ca50c68f882a
	[BZ #17711]
	* config.make.in (have-protected-data): New.
	* configure.ac: Check linker support for protected data symbol.
	* configure: Regenerated.
	* elf/Makefile (modules-names): Add tst-protected1moda and
	tst-protected1modb if $(have-protected-data) is yes.
	(tests): Add tst-protected1a and tst-protected1b if
	$(have-protected-data) is yes.
	($(objpfx)tst-protected1a): New.
	($(objpfx)tst-protected1b): Likewise.
	(tst-protected1modb.so-no-z-defs): Likewise.
	* elf/tst-protected1a.c: New file.
	* elf/tst-protected1b.c: Likewise.
	* elf/tst-protected1mod.h: Likewise.
	* elf/tst-protected1moda.c: Likewise.
	* elf/tst-protected1modb.c: Likewise.