Move replaceLinkHolders() from OutputPage to Parser, because

Move replaceLinkHolders() from OutputPage to Parser, because
it needs to happen before unstripNoWiki() and before tidy.
This also makes the parser more self-contained, so there is
no need to create an OutputPage object for the parser
tester.

Call unstripNoWiki() before creating a Title object
for an internal link; this fixes <nowiki> inside of
a link target. Need to make sure this does not degrade
performance.