Updated: cygwin-1.7.0-31

[Christopher Faylor]

Incomplete list of changes since 1.7.0-29:

- Compiled with gcc4.

- Stop considering .bat an executable path.

- Fixes for group confusion between /etc/passwd and /etc/group.

- Make sure that threads created for timer calls are started in detached
state.

- Fix problems with cygcheck which caused premature termination when
cygwin1.dll was unloaded.

- Fix behavior of pthread mutexes after a fork.

- Fix some pipe read problems.