[mythtv] minor build issues with mfd

[Dave Caplinger]

I noticed just a few odd things while trying to build the new mfd module
- I'm not sure I'm proficient enough yet to submit a patch for this, but
the description is simple:

1) In the Makefile generated by qmake, the SUBTARGETS needs to be
re-ordered to make sure that sub-mfdlib gets built before the rest since
they try to link to it.  (I modified the Makefile directly but I'm sure
there's a "right" way to fix this that involves qmake somehow.)

2) in mfd/plugins/dappserver/httpd_persistent, the file
"http_persistent.pro" should be renamed to "httpd_persistent.pro".

Once these two minor changes are made, mfd will build.  (I have no idea
just yet if it *works*, but I'm getting there... :-)

- Dave