install sphinx-generated manpages

install sphinx-generated manpages

Install sphinx-generated manpages.  Original nroff manpages remain for
reference until proofreading is complete.  Modify
doc/rst_source/conf.py to better deal with shadow manpages -- sphinx
will now build k5login.5 instead of .k5login.5, and kadmin.1 instead
of both kadmin.1 and kadmin.local.8.

Proofreaders should ensure that the original nroff manpages (and
associated Makefile rules) are deleted once their reST format
equivalents have been proofread.

ticket: 7064
status: open

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@25625 dc483132-0cff-0310-8789-dd5450dbe970