compiler: report error for ++/-- applied to a non-numeric type

This avoids a compiler crash.

Fixes GCC PR 83071.

Change-Id: I199f5e0277bea3a4aca834ff4afd56c92a194361
Reviewed-on: https://go-review.googlesource.com/78875
Reviewed-by: Than McIntosh <thanm@google.com>
1 file changed