libstdc++: Fix names.cc test failures on Windows

libstdc++: Fix names.cc test failures on Windows

The Windows CRT headers define structs with members called f, x, y etc
so don't check those. There are also lots of unnecessary function
parameters in mingw headers using non-reserved names, e.g.

<time.h> uses p and z as parameters of mingw_gettimeofday
<inttypes.h> uses j as a parameter of imaxabs
<pthread.h> uses l, o and func as parameter names

Those should be fixed in the headers instead.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:

	* testsuite/17_intro/names.cc: Adjust for Windows.