Buildbot: give 20 minute per test file

It seems like at least 2 buildbots need more than 15 minutes per test file.
Example with "AMD64 Snow Leop 3.x":

    10 slowest tests:
    - test_tools: 14 min 40 sec
    - test_tokenize: 11 min 57 sec
    - test_datetime: 11 min 25 sec
    - ...

Makefile.pre.in

@@ -988,7 +988,7 @@ $(LIBRARY_OBJS) $(MODOBJS) Programs/python.o: $(PYTHON_HEADERS)
 TESTOPTS=	$(EXTRATESTOPTS)
 TESTPYTHON=	$(RUNSHARED) ./$(BUILDPYTHON) $(TESTPYTHONOPTS)
 TESTRUNNER=	$(TESTPYTHON) $(srcdir)/Tools/scripts/run_tests.py
-TESTTIMEOUT=	900
+TESTTIMEOUT=	1200
 
 # Run a basic set of regression tests.
 # This excludes some tests that are particularly resource-intensive.

Tools/buildbot/test.bat

@@ -16,4 +16,4 @@ if "%1"=="+q" (set rt_opts=%rt_opts:-q=%) & shift & goto CheckOpts
 if NOT "%1"=="" (set regrtest_args=%regrtest_args% %1) & shift & goto CheckOpts
 
 echo on
-call "%here%..\..\PCbuild\rt.bat" %rt_opts% -uall -rwW --slowest --timeout=900 %regrtest_args%
+call "%here%..\..\PCbuild\rt.bat" %rt_opts% -uall -rwW --slowest --timeout=1200 %regrtest_args%