Make test suite work better when the temp directory is on NFS.

Deleting directories is one of the great unsolved problems of CS, thanks to
abominations like NFS lock files and Windows and races with other processes
cleaning up after themselves in the background. The gpg test harness
sometimes failed to delete its temp directory on NFS. Avoid the problem
class by not deleting it at all, and putting it inside the tmp repo being
tested. The test suite's more robust (and/or nonsensical) workarounds for
deleting its test dir will thus be used, hopefully avoiding the problem
until an OS finds a new way to violate POSIX and the laws of nature.

Note that this means that the .gnupg directory will be on whatever
filesystem the test suite is being run on, which may be a lesser quality
filesystem than gpg is really expecting. Gpg does not seem to need to
write sockets etc to there so this seems ok. The only known problem is
that if the filesystem forces a directory mode like 777, gpg will warn
about unsafe home directory perms, but it still works.

Utility/FileMode.hs

@@ -69,6 +69,7 @@ otherGroupModes :: [FileMode]
 otherGroupModes = 
 	[ groupReadMode, otherReadMode
 	, groupWriteMode, otherWriteMode
+	, groupExecuteMode, otherExecuteMode
 	]
 
 {- Removes the write bits from a file. -}