PR 21274, ld segfaults linking PE DLL

PR 21274, ld segfaults linking PE DLL

Don't use fixed size buffers for symbol names.

	PR 21274
	PR 18466
	* emultempl/pe.em (pe_find_data_imports): Don't use fixed size
	symbol buffer.  Instead, xmalloc max size needed with space for
	prefix.  Wrap overlong lines.  Formatting.  Pass symbol buffer
	copy of name to pe_walk_relocs_of_symbol.
	(make_inport_fixup): Add "name" param, pass to pe_create_import_fixup.
	* emultempl/pe.em (pep_find_data_imports): As for pe_find_data_imports.
	(make_import_fixup): Add "name" param, pass to pep_create_import_fixup.
	Use bfd_get_signed_* and remove unnecessary casts.  Formatting.
	* pe-dll.c (pe_walk_relocs_of_symbol): Add "name" param.  Pass to
	callback.
	(make_import_fixup_mark): Add "name" param.  Make use of prefix
	space rather than xmalloc here.
	(pe_create_import_fixup): Likewise.
	* pe-dll.h (pe_walk_relocs_of_symbol): Update prototype.
	(pe_create_import_fixup): Likewise.
	* pep-dll.h (pep_walk_relocs_of_symbol): Likewise.
	(pep_create_import_fixup): Likewise.