Issue 5354: Change API for import_fresh_module() to better support test_warnings use case (also fixes some bugs in the original implementation)

int, long, and float __format__(), and it keeps their implementation
in sync with py3k.

Also added PyOS_double_to_string. This is the "fallback" version
that's also available in trunk, and should be kept in sync with that
code. I'll add an issue to document PyOS_double_to_string in the C
API.

There are many internal cleanups. Externally visible changes include:

- Implement PEP 378, Format Specifier for Thousands Separator, for
  floats, ints, and longs.

- Issue #5515: 'n' formatting for ints, longs, and floats handles
  leading zero formatting poorly.

- Issue #5772: For float.__format__, don't add a trailing ".0" if
  we're using no type code and we have an exponent.

test_support.import_module on the appropriate modules
before any other imports.

correctly rounded, using round-half-to-even.  This ensures that the
value of float(n) doesn't depend on whether we're using 15-bit digits
or 30-bit digits for Python longs.

is deprecated.  Use an explicit int() instead.

Make _pagesize static.

env parameter that on Windows SystemRoot is required in order
to run side-by-side assemblies.

tests by R. David Murray