[PATCH][ARM] Fix extern protected data handling

[Szabolcs Nagy]

Emit *GLOB_DAT instead of *RELATIVE relocs for protected data
in shared objects.

This is needed for the fix of glibc bug 17711:
https://sourceware.org/bugzilla/show_bug.cgi?id=17711

bfd/ChangeLog:

2015-07-22  Szabolcs Nagy  <szabolcs.nagy@arm.com>

	PR ld/18705
	* elf32-arm.c (elf_backend_extern_protected_data): Define.

ld/testsuite/ChangeLog:

2015-07-22  Szabolcs Nagy  <szabolcs.nagy@arm.com>

	PR ld/18705
	ld-arm/protected-data.d: New.
	ld-arm/protected-data.s: New.
	ld-arm/arm-elf.exp: Add new test.