doxygen produces *_src_* 'man' pages

[Vince Weaver]

From Steve Kaufmann:

I find that when I build man pages manually I get "src" .1 files that are not man pages but are .1 files based on the "src" and "src/utils" directories under papi/src. This must be an artifact of doxygen or doxygen is not configured correctly to ignore the directories. To avoid having these bogus files installed I simply updated the doc/Makefile to remove them after doxygen was executred: