configure.host: Use config/os/mingw32-w64 instead of config/os/mingw32 if vendor...

configure.host: Use config/os/mingw32-w64 instead of config/os/mingw32 if vendor key is "w64".

2011-10-14  Jonathan Yong  <jon_y@users.sourceforge.net>

	* configure.host: Use config/os/mingw32-w64 instead of
	config/os/mingw32 if vendor key is "w64".
	* config/os/mingw32-w64: Duplicate from config/os/mingw32.
	* config/os/mingw32-w64/os_defines.h: Enable
	_GLIBCXX_FULLY_DYNAMIC_STRING if undefined.
	* acinclude.m4: Set fully-dynamic-string to 1 when enabled,
	0 when disabled or undefined if unset by user.
	* include/bits/basic_string.h: Check if
	_GLIBCXX_FULLY_DYNAMIC_STRING is set to 0 instead of undefined.
	include/bits/basic_string.tcc: Likewise.
	* configure: Regenerated.
	* config.h.in: Likewise.

From-SVN: r179961