Bug 902619 - Write mozinfo.json as part of config.status; r=ted

There are both mechanical and logical changes in this patch.

The mechanical changes involve moving some files into the mozbuild
package.

The logical changes include move writing of mozinfo.json into
config.status (from configure.in). There were some variable assignments
being performed in configure.in. These variables were read from
writemozinfo.py. However, these variables don't appear to be necessary!
Now that mozinfo has full access to the underlying config.status data
structure, it can now access these variables directly. I verified that
every variable being assigned in configure.in had a corresponding
AC_SUBST earlier in the file.

The only variable that's a bit weird is the TOPSRCDIR and MOZCONFIG
environment variables. mozinfo continues to look in the environment for
MOZCONFIG. However TOPSRCDIR is now coming from config.status.

As part of moving the code, I also modernized the test file, cleaned up
some style, and removed some unused imports.

--HG--
rename : config/writemozinfo.py => python/mozbuild/mozbuild/mozinfo.py
rename : config/tests/unit-writemozinfo.py => python/mozbuild/mozbuild/test/test_mozinfo.py
Bug 902609 - Make xpcshell.ini manifest strict mode compliant; r=ahal