[PATCH] Fix format_pieces selftest on Windows

[Tom Tromey]

>>>>> "Tom" == Tom Tromey via Gdb-patches <gdb-patches@sourceware.org> writes:

Tom> The format_pieces selftest currently fails on Windows hosts.
Tom> The selftest doesn't handle the "%ll" -> "%I64" rewrite that the
Tom> formatter may perform, but also gdbsupport was missing a configure
Tom> check for PRINTF_HAS_LONG_LONG.  This patch fixes both issues.

I'm checking this in.

Tom