Patch by Michael Ensslin.

Patch by Michael Ensslin.

Based on patch by Martin Panter.

Based on patch by Martin Panter.

All the new information in 3.4's readme.txt was already here, but the
wrong name was used to refer to the script.  Also reworded the sentence.

It now recommends PCbuild/get_externals.bat instead of the scripts in
Tools/buildbot.

I would just outright delete them, but the readme in PCbuild recommended
their use, so I figure it would be nice to leave them there for a while.

Related Issues:

#issue21528
#issue24453

and set comparisions.  Patch by Gareth Rees.

* Don't use the timestamp of an existing file anymore, only use fixed
  timestamp
* Enhance the code checking the resolution of the filesystem timestamps.
* Check timestamps with a resolution of 1 microsecond instead of 1 millisecond
* When os.utime() uses the current system clock, tolerate a delta of 20 ms.
  Before some os.utime() tolerated a different of 10 seconds.
* Merge duplicated tests and simplify the code

* Don't use the timestamp of an existing file anymore, only use fixed
  timestamp
* Enhance the code checking the resolution of the filesystem timestamps.
* Check timestamps with a resolution of 1 microsecond instead of 1 millisecond
* When os.utime() uses the current system clock, tolerate a delta of 20 ms.
  Before some os.utime() tolerated a different of 10 seconds.
* Merge duplicated tests and simplify the code

This is mostly a backport of issue #21907, but also includes a few
extras necessary to make the bulidbot scripts as thin as possible.

  string.Template instances.

  string.Template instances.