Handle 8-bit characters under LOCALE=C

Even when the character set is specified as ASCII, we should handle data
outside the 7-bit range gracefully by simply copying it, even if it is
technically no longer ASCII.

This fixes several of Git for Windows' tests, e.g. t7400.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

winsup/cygwin/strfuncs.cc

@@ -1146,7 +1146,11 @@ _sys_mbstowcs (mbtowc_p f_mbtowc, wchar_t *dst, size_t dlen, const char *src,
 	     to store them in a symmetric way. */
 	  bytes = 1;
 	  if (dst)
+#ifdef STRICTLY_7BIT_ASCII
 	    *ptr = L'\xf000' | *pmbs;
+#else
+	    *ptr = *pmbs;
+#endif
 	  memset (&ps, 0, sizeof ps);
 	}