start_psymtab_common takes references to the global_psymbols and
static_psymbols vectors, but it also has an objfile parameter.  This
is redundant, so this patch simplifies the function by removing those
reference parameters.

gdb/ChangeLog
2019-01-10  Tom Tromey  <tom@tromey.com>

	* xcoffread.c (xcoff_start_psymtab): Remove global_psymbols and
	static_psymbols parameters.
	(scan_xcoff_symtab): Update.
	* psymtab.c (start_psymtab_common): Remove global_psymbols and
	static_psymbols parameters.
	* psympriv.h (start_psymtab_common): Update.
	* mdebugread.c (parse_partial_symbols): Update.
	* dwarf2read.c (create_partial_symtab): Update.
	* dbxread.c (read_dbx_symtab): Update.
	(start_psymtab): Remove global_psymbols and static_psymbols
	parameters.