tic54x set_arch_mach

tic54x set_arch_mach

The tic54x backend provides its own coff_set_arch_mach, but wants to
use the standard coff_set_section_contents.  BFD_JUMP_TABLE_WRITE
defines both of these functions, so the code also provides a wrapper
for coff_set_section_contents.  This is all quite OK, but I was on a
mission to remove unnecessary declarations in coffcode.h, and on
deleting the one for coff_set_arch_mach ran into a warning about the
function being unused.  I could have kept that declaration with its
ATTRIBUTE_UNUSED or written "static bool ATTRIBUTE_UNUSED" on the
definition but the latter is not usual and looks odd to me.  So I
had a closer look at tic54x_set_arch_mach and decided the function is
very likely wrong to allow bfd_arch_unknown.  Thus the backend should
be using the standard coff_set_arch_mach.

	* coff-tic54x.c: Use BFD_JUMP_TABLE_WRITE (coff) in target vecs.
	(tic54x_coff_set_arch_mach): Delete.
	(tic54x_set_section_contents): Delete.
	* coffcode.h: Delete unnecessary forward declarations.