2015-05-07  Yao Qi  <yao@codesourcery.com>
	    Sandra Loosemore  <sandra@codesourcery.com>

	Avoid segfault on missing directory table.

	gdb/
	* dwarf2read.c (setup_type_unit_groups): Do NULL pointer check
	to 'lh->include_dirs' before accessing to it.
	(psymtab_include_file_name): Likewise.
	(dwarf_decode_lines_1): Likewise.
	(dwarf_decode_lines): Likewise.
	(file_file_name): Likewise.