The man pages are generated using tools from http://wgropp.cs.illinois.edu/projects/software/sowing/
Install sowing tools like follows:
./configure --prefix=</path/to/install>
make && make install
export PATH=</path/to/install>/bin:$PATH
export DOCTEXT_PATH=</path/to/install>/share/doctext
After installation, run the following in your MPICH source directory.
make mandoc && make install