Tests: Verify policies are introduced only in "official" versions

Add the CMake.PolicyCheck test.

This test uses "git grep" to look for policies added in a "dated"
version of CMake. It will fail if a policy is added as of,
for example, CMake 2.8.11.20130828.

The intent is to prevent such constructs from making it into an
"official" release. Three instances actually appeared in the first
attempted release candidate for 2.8.12.

This test may sometimes yield false positives. After all, it's just
using a regular expression to detect this condition, and something
in a comment could possibly match it. As of right now, that's not
true, but it's easy to imagine such a comment being added.

The new test may also not catch all future problems of this sort.
However, it will catch problems of this sort for all code that follows
the present layout style in Source/cmPolicies.cxx.
CMake Nightly Date Stamp
CMakePackageConfigHelpers: Add a find_dependency macro

This macro handles the EXACT, REQUIRED and QUIET options
and sets an appropriate NOT_FOUND_MESSAGE for the package
if a dependency is not found.
Merge topic 'add-find_dependency-macro' into next

bb501a2 CMakePackageConfigHelpers: Add a find_dependency macro
Merge topic 'normalize-system-includes-check'

5e15f39 Normalize system directories from the interface target property
Merge topic 'ctest-gtm-coverage-fileoffset-bug'

782eba3 CTest: Fix GTM coverage parsing line offset bug
Merge branch 'master' into next
Merge topic 'add-policy-version-test' into next

b494722 Tests: Verify policies are introduced only in "official" versions