sepolicy: Define and allow map permission

Kernel commit 3ba4bf5f1e2c ("selinux: add a map permission check for mmap")
added a map permission check on mmap so that we can
distinguish memory mapped access (since it has different implications
for revocation).  The purpose of a separate map permission check on
mmap(2) is to permit policy to prohibit memory mapping of specific files
for which we need to ensure that every access is revalidated, particularly
useful for scenarios where we expect the file to be relabeled at runtime
in order to reflect state changes (e.g. cross-domain solution, assured
pipeline without data copying).  The kernel commit is anticipated to
be included in Linux 4.13.

This change defines map permission for the Android policy.  It mirrors
the definition in the kernel classmap by adding it to the common
definitions for files and sockets.  This will break compatibility for
kernels that predate the dynamic class/perm mapping support (< 2.6.33);
on such kernels, one would instead need to add map permission
to the end of each file and socket access vector.

This change also adds map permission to the global macro definitions for
file permissions, thereby allowing it in any allow rule that uses these
macros, and to specific rules allowing mapping of files from /system
and executable types. This should cover most cases where it is needed,
although it may still need to be added to specific allow rules when the
global macros are not used.

Test: Policy builds

Change-Id: Iab3ccd2b6587618e68ecab58218838749fe5e7f5
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>