gdb/

gdb/
	PR 12573
	* dwarf2read.c (struct dwarf2_cu): New field has_loclist.
	(producer_is_gcc_ge_4_0): New function.
	(process_full_comp_unit): Set also symtab->locations_valid.  Move the
	symtab->language code.
	(var_decode_location): Set cu->has_loclist.
	* symtab.c (skip_prologue_sal): New variables saved_pc, force_skip and
	skip.  Intialize force_skip from locations_valid.  Move the prologue
	skipping code into two passes.
	* symtab.h (struct symtab): Make the primary field a bitfield.  New
	field locations_valid.

gdb/testsuite/
	PR 12573
	* gdb.dwarf2/dw2-skip-prologue.S: New file.
	* gdb.dwarf2/dw2-skip-prologue.c: New file.
	* gdb.dwarf2/dw2-skip-prologue.exp: New file.