gdb/

gdb/
	* elfread.c (elf_symfile_read): Protect dwarf2_initialize_objfile by
	!objfile_has_partial_symbols.  New comment.
	* objfiles.c (objfile_has_partial_symbols): Call HAS_SYMBOLS if
	SYM_READ_PSYMBOLS is not present. Extend the comment.
	* symfile.h (struct sym_fns): Extend the sym_read_psymbols comment.

gdb/testsuite/
	* gdb.base/gdbindex-stabs-dwarf.c: New file.
	* gdb.base/gdbindex-stabs.c: New file.
	* gdb.base/gdbindex-stabs.exp: New file.