This patch to the Go frontend implements better checks for constants
passed to the predefined function make.  It gives an error for using
negative numbers, and when the length is larger than the capacity.
These are required by the language spec, but were never enforced by the
compiler until now.  This required updating one test case.  Bootstrapped
and ran Go testsuite on x86_64-unknown-linux-gnu.  Committed to
mainline.

Ian