Stop phpDocParam highlight leakage

Problem:  The new Java-like syntax highligting added phpDocComment, et
al.  However phpDocParams highlighted indented html tags in a file with
no doc comments.

Fix: Mark phpDocParams as contained, so phpDocParams must reside in
phpDocComments to receive vim highlights.

Signed-off-by: Justin Charette <charetjc@gmail.com>
Merge remote-tracking branch 'boxofrox/fix/php-tag-recognition'
Restore spell-checking in docblock comments.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	syntax/php.template
	syntax/php.vim

Attempted to merge in upstream changes as they claimed to have fixed an issue
that broke spell checking presumably introduced by my branch. I was unable to
get spell checking working with the syntax file that was part of my original
fork: https://github.com/StanAngeloff/php.vim/commit/36ccde52967f56ea0eed2f8a1fe6d1236cc1df96

Because of this I left my script as is in favor of highlighting just the
@attribute part of the docblock and not highlighting the entire comment string
which appeared visually awkward to me. Ideally I'd love to get spell checking
working in all the places that it should be working but that seems to be a
bigger issue all together.

Also added support for the @usage attribute as it's something that is fairly
common albeit not standard docblocking