gdtoa: Sync to match the latest version at netlib.org as of Nov. 02
2011.  Changelog from http://netlib.org/fp/changes :
    Add field int_max to struct FPI and adjust gdtoa.c and *fmt.c
    so gdtoa.c tests against fpi->int_max rather than Int_max. This
    only affects some conversions by g_ffmt.c, which in some cases
    produced too many digits.

git-svn-id: svn+ssh://svn.code.sf.net/p/mingw-w64/code/trunk@4577 4407c894-4637-0410-b4f5-ada5f102cad1