util: fix the check for non-C99 compilers (issue4605)

histedit: fix rollup prompting for a commit message (issue4606) Commit 090da03361c5 broke histedit's rollup by causing it to open the editor. Turns out I missed a spot where the rollup option was read. This fixes that and adjusts the test to catch this case.

test-hook.t: don't directly use redirect to /dev/null in hook for Windows This goes with 57f1dbc99631. External hooks are run in cmd.exe, which doesn't know about /dev/null, but sh can handle it.

mq: avoid silent failure when single patch doesn't apply (issue4604) The error-handling here is quite byzantine. self._apply raises an AbortNoCleanup, but self.apply was swallowing the exception and returns 2. In self.push, we catch all exceptions.. and cleanup. We try to print a message to clean up.. but that relies on having a top-of-stack. Instead, we re-raise the abort in self.apply, and avoid cleanup on AbortNoCleanup in self.push by adding a trivial new except clause. We also modernize the now-visible abort message.

pushkey: flush pending data before running a pre-pushkey hook (issue4607) The pre-pushkey hook will likely validate the pushkey based on element previously changed in the same transaction. We need to make theses data available for the hook.

pushkey: use hook arguments from transaction when one exists When pushkey is called during a transaction, we include its 'hookargs' when running the pre-pushkey hooks. Having more data cannot hurt, especially the transaction ID.

util.h: also sniff for C99 before trying to use stdbool.h (issue4605) stdbool.h isn't required until C99. Sigh.

changelog: fix readpending if no pending data exist (issue4609) Since transaction are used for more than just changesets, it is possible to have a transaction without new changesets at all. In this case no ''00changelog.i.a' are written. In all cases the 'changelog.readpending' method is called if the repository has any pending data. The 'revlog' logic provides empty content if the file is missing, so the whole operation resulted in an empty changelog. We now skip reading the pending file if it is missing.

afterlock: add the callback to the top level lock (issue4608) If 'wlock' is taken, we should add 'afterlock' callback to the 'wlock' instead. Otherwise, running post transaction hook after 'lock' is release but 'wlock' is still taken lead to a deadlock (eg: 'hg update' during a hook). This situation is much more common since: 5dc5cd7abbf5 push: acquire local 'wlock' if "pushback" is expected (BC) (issue4596)

debuglock: access the lock file using the proper vfs Before this fix, 'wlock' was always reported as "free" because '.hg/store/wlock' have never been a thing.