d: Fix junk in generated symbol on powerpc64-*-* [PR98921]

d: Fix junk in generated symbol on powerpc64-*-* [PR98921]

This adds a special formatter to OutBuffer to handle formatted printing
of integers, a common case.  The replacement is faster and safer.

In dmangle.c, it also gets rid of a number of problematic casts, as seen
on powerpc64 targets.

gcc/d/ChangeLog:

	PR d/98921
	* dmd/dmangle.c (Mangler::visit (TypeSArray *)): Use buf->print
	  to format integer value.
	(Mangler::visit (TypeIdentifier *)): Likewise.
	(Mangler::toBuffer): Likewise.
	(Mangler::visit (IntegerExp *)): Likewise.
	(Mangler::visit (StringExp *)): Likewise.
	(Mangler::visit (ArrayLiteralExp *)): Likewise.
	(Mangler::visit (AssocArrayLiteralExp *)): Likewise.
	(Mangler::visit (StructLiteralExp *)): Likewise.
	* dmd/root/outbuffer.c (OutBuffer::print): New function.
	* dmd/root/outbuffer.h (OutBuffer::print): Declare.

(cherry picked from commit 6a481021a65d6237b0c509a76fcd9c1f32c4558e)