Man page export from the wrapper binary.

Man page export from the wrapper binary.

Implement nroff output format for 'gmx help -export'.
Move the header/footer generation out of wman.cpp.
The generation is now off by default.  Can be reinstantiated if someone
comes with a good approach for the case where the compiled binaries
don't run on the build host (e.g., compiling AVX256 binaries on a SSE4.1
host).

Related to #685 and #969.

Change-Id: I17725e3a487470bea8f6db2a59da31139e70621e