[tree-ssa] build failure on powerpc-aix in libobjc

[David Edelsohn]

>>>>> Andrew Pinski writes:

Andrew> On powerpc-aix (this was reported to me from David Edelsohn),
Andrew> isdigit is not a macro so fold_builtin is folding isdigit and
Andrew> it causes an ICE.  Since the folding of isdigit is new, it
Andrew> looks like it does check if we are able to create non
Andrew> gimple which it happens here.

	The specific ICE is:

error: Invalid operand to binary operator
(unsigned int<D3>)T.217<D4528> - 48;
internal compiler error: verify_stmts failed.