[PATCH 0 of 3] mq.patchheader refactoring and more

[Steve Losh]

This series of patches is an attempt to clean up the patchheader class in
mq.py. My goal is to make it more readable and more robust when dealing with
various types of patch headers.

The first patch in the series just adds any() and all() functions to
mercurial/util.py. These are built-in functions that were added in 2.5 so we
can't use them yet. They're very useful and can make code much easier to read.

The second patch is the actual refactoring of patchheader. The documentation I
added to the module's docstring probably needs some work, and I'm sure I
missed some coding-style things along the way. I updated a lot of the test
output, but that was only to reflect the new (more consistent) ordering the
the headers -- no functionality should have changed.

The third patch combines test-mq-header-from and test-mq-header-date into on
file: test-mq-headers. Now that the Parent IDs are included in hg-style MQ
patches it makes more sense to test all the headers at once so we can cover
all the possible combinations.

This third patch also completely refactors the header tests to provide much,
much more comprehensive testing of the possible combinations of headers.
Unfortunately it increases the run time of the header tests from ~22 seconds
to ~74 seconds (on my laptop).

I'm not sure if that's too much of a performance hit for these tests that
cover a less-than-critical part of the code. Even if this patch doesn't go
into core it I'm glad I did it to test my patchheader refactoring.