Fix a segmentation fault triggered when trying to handle an unresolved PE symbol...

Fix a segmentation fault triggered when trying to handle an unresolved PE symbol with a very long name.

	PR ld/18466
	* emultempl/pe.em (pe_find_data_imports): Generate an error if a
	symbol name is too long to handle.
	* emultempl/pep.em (pep_find_data_imports): Likewise.