Report category names via the xml help output (but not, yet,
during 'normal' help output).

R=ncalvin
DELTA=3  (3 added, 0 deleted, 0 changed)


Revision created by MOE tool push_codebase.
MOE_MIGRATION=3066


git-svn-id: https://gflags.googlecode.com/svn/trunk@63 6586e3c6-dcc4-952a-343f-ff74eb82781d