[pushed] modula2: add modula-2 language section to languages supported by GCC

[Gaius Mulley]

Pushed to trunk as r14-9915-g0dc39dee836761f1bc993d760f4ed5f3d127897a

This patch introduces a small modula-2 language section to the
Language Standards Supported by GCC node.

gcc/ChangeLog:

        * doc/standards.texi (Language Standards Supported by GCC):
        Add Modula-2 language section.