test-logtoprocess: don't run on Windows

Several bits of output were missing[1], unless the DETACHED_PROCESS flag is
_not_ passed to subprocess.Popen().  The problem with that is it briefly opens
and closes several cmd.exe windows on screen.  Foozy also mentioned some other
issues in that thread.

With this, the last of the long standing Windows failures fixed, the test suite
now runs cleanly (536 ran, 67 skipped) on Windows 7 x64, with python 2.7.13. \o/

[1] https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-April/096987.html

tests/test-logtoprocess.t

@@ -1,3 +1,5 b''
+#require no-windows
+
 ATTENTION: logtoprocess runs commands asynchronously. Be sure to append "| cat"
 to hg commands, to wait for the output, if you want to test its output.
 Otherwise the test will be flaky.