Hi,

This is again an independent portion of the bitpos patch[1].  The
variables used to set up the stack are currently int, which may not be
sufficient for larger types.  This patch expands the variable sizes to
ssize_t.  The patch also adds an additional validation to check for
underflow in the value of the stack pointer after pushing the
arguments.  I don't have any means to run any tests, so I have only
done a compile test for this by configuring with --enable-targets=all.
Does this look safe for commit?

Regards,
Siddhesh

[1] http://sourceware.org/ml/gdb-patches/2012-08/msg00144.html

gdb/ChangeLog:

	* alpha-tdep.c (alpha_push_dummy_call): Expand ACCUMULATE_SIZE,
	REQUIRED_ARG_REGS, OFFSET, LEN, TLEN to ssize_t.  Check for
	underflow in SP.
	(struct alpha_arg): Expand members LEN, OFFSET to ssize_t.