gdb: convert arc to new-style debug macros

gdb: convert arc to new-style debug macros

Add the standard arc_debug_printf, but also arc_linux_debug_printf,
arc_linux_nat_debug_printf and arc_newlib_debug_printf to match the
prefixes currently used in the debug messages.

gdb/ChangeLog:

	* arc-tdep.h (arc_debug_printf): New.
	* arc-tdep.c: Use arc_debug_printf.
	* arc-linux-nat.c (arc_linux_nat_debug_printf): Add and use.
	* arc-linux-tdep.c (arc_linux_debug_printf): Add and use.
	* arc-newlib-tdep.c (arc_newlib_debug_printf): Add and use.

Change-Id: I5d937566ed7a1925f7982e8809802c8f0560d8c6