tests/test-simplemerge.py.out

cext: extract revlog/index parsing code to own C file

parsers.c is ~3000 lines and ~2/3 of it is related to the revlog
index type.

We already have separate C source files for directory utilities
and manifest parsing. I think the quite unwieldy revlog/index
parsing code should be self-contained as well.

I performed the extraction as a file copy then removed content
from both sides in order to preserve file history and blame.

As part of this, I also had to move the hexdigit table and
function to a shared header since it is used by both parsers.c
and revlog.c

# no-check-commit

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Ran 16 tests in 0.000s

OK