rddbg.c stabs FIXMEs

This should sort out some very old FIXMEs in code handling stabs
debug info.  Necessary if we are to fuss over freeing up memory before
objdump and objcopy exit.  It is of course better from a user
viewpoint to *not* free memory, which takes some time, and leave that
to process exit.  The only reason to do so is that having many memory
leaks in binutils/ code tends to hide leaks in bfd/ or opcodes/, which
we should care about.

	* budbg.h (parse_stab): Update prototype.
	* debug.h (debug_start_source): Update prototype.
	* debug.c (debug_start_source): Add name_used.  Set if stashed.
	* rddbg.c (read_symbol_stabs_debugging_info): Always malloc
	stab string passed to parse_stab.  Free stab string when
	unreferenced.
	(read_section_stabs_debugging_info): Likewise, and strings
	section contents.
	* stabs.c (parse_stab): Add string_used param.  Set if string
	stashed.  Pass to debug_start_source.  Realloc file_types
	array rather that using malloc.  Clarify comment about
	debug_make_indirect_type.