[gcc] Remove old "nc" cases from libstdc++'s configure script

These cases are not used, and were apparently added by changing the
generated file rather than editing the source, configure.ac.
Re-running autoconf 2.59 undoes them.

BUG=http://code.google.com/p/nativeclient/issues/detail?id=660

Review URL: http://codereview.chromium.org/3186025
1 file changed