This is the moral equivalent of

  git/git@39a87a29ce364ed3337e535adce5973731ba2968

from Adrian Johnson <ajohnson@redneon.com>.

This pulls upstream changes from:

  git/git@8a2e8da367f7175465118510b474ad365161d6b1

  git/git@abf8f9860248d8c213600974742f18dadaa8fbb5

  git/git@407e07f2a6f55e605fda9e90cb622887269f68b5

all by Johannes Sixt <j6t@kdbg.org>.

Writing a sample Javascript driver pointed out some extra
whitespace handling that needed to be done in the diff driver.
This adds some tests with some sample javascript code that I
pulled off of GitHub just to see what would happen.  Also, to
clean up the userdiff test data, I did a "git gc" and packed
up the test objects.

Since I don't have permission yet on the code from Git, I decided
I'd take a stab at writing patterns for PHP and Javascript myself.
I think these are pretty weak, but probably better than the
default behavior without them.

This brings over the Pascal and CSharp userdiff data.

I contacted a number of Git authors and lined up their permission
to relicense their work for use in libgit2 and copied over their
code for diff driver xfuncname patterns.  At this point, the code
I've copied is taken verbatim from core Git although Thomas Rast
warned me that the C++ patterns, at least, really need an update.
I've left off patterns where I don't feel like I have permission
at this point until I hear from more authors.