Cygwin: path_conv: decouple pathconv_flags from path_types

There's an unfortunate amalgamation of caller-provided pathconv_arg
flags with path_types flags which in turn are mostly mount flags.

This leads to a confusion of flag values in sylink_info::pflags and,
in turn, in path_conv::path_flags.

This patch decouples pathconv_flags from the other flags by making
sure that a pathconv_flag is never copied into a variable used for
path_types flags.  Also, remove PATH_NO_ACCESS_CHECK since it's
not necessary.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/path.h

@@ -39,6 +39,8 @@ struct suffix_info
 
 extern suffix_info stat_suffixes[];
 
+/* DO NOT copy any of these files into the same set of flags as the
+   below path_types.  Ever. */
 enum pathconv_arg
 {
   PC_SYM_FOLLOW		= 0x0001,
@@ -76,7 +78,6 @@ enum path_types
   PATH_DOS		= MOUNT_DOS,
   PATH_IHASH		= MOUNT_IHASH,
   PATH_ALL_EXEC		= (PATH_CYGWIN_EXEC | PATH_EXEC),
-  PATH_NO_ACCESS_CHECK	= PC_NO_ACCESS_CHECK,
   PATH_CTTY		= 0x00400000,	/* could later be used as ctty */
   PATH_OPEN		= 0x00800000,	/* use open semantics */
   					/* FIXME?  PATH_OPEN collides with