tweak __ehdr_start visibility and flags for check_relocs

bfd/
	* elf-bfd.h (UNDEFWEAK_NO_DYNAMIC_RELOC): Test linker_def.
ld/
	* ldelf.c (ldelf_before_allocation): Don't force __ehdr_start
	local and hidden here..
	* ldlang.c (lang_symbol_tweaks): ..do so here instead and set
	def_regular and linker_def for check_relocs.  New function
	extracted from lang_process.
3 files changed