Prettify output of debug_dwarf_die

Prettify output of debug_dwarf_die

When debugging gcc, I tried calling debug_dwarf_die and I saw this
output:

      DW_AT_location: location descriptor:
        (0x7fffe9c2e870) DW_OP_dup 0, 0
        (0x7fffe9c2e8c0) DW_OP_bra location descriptor (0x7fffe9c2e640)
, 0
        (0x7fffe9c2e820) DW_OP_lit4 4, 0
        (0x7fffe9c2e910) DW_OP_skip location descriptor (0x7fffe9c2e9b0)
, 0
        (0x7fffe9c2e640) DW_OP_dup 0, 0

I think those ", 0" should not appear on their own lines.  The issue
seems to be that print_dw_val should not generally emit a newline,
except when recursing.

gcc/ChangeLog

	* dwarf2out.cc (print_dw_val) <dw_val_class_loc>: Don't
	print newline when not recursing.