minor bugs in 2.1.14

[Moore, Joe]

A couple of minor problems I've found building cfengine-2.1.14 on
Solaris 7 with the Workshop C compiler v5.0*...

cf.extern.h line 45 gives an error of "empty declaration" because there
are two consecutive ;'s.

proto.c line 430 uses C++-style comments (//) which is not C-compatible.

methods.c line 310 uses C++-stlye comments too.

Probably nobody else notices these things since they are acceptable
under gcc, but they're pretty trivial.

--Joe
* Lowest common denominator in this environment...