GNUtoMS: Add support for VS 2013 (#14936)

Add to the Platform/Windows-GNU module list of VS registry entries those
for VS 2013.  Also add the name "vcvars64.bat" used by VS 10 and above
for 64-bit tools.
FindFreetype: Add newlines to reduce code width

This also makes argument lists easier to update.
FindFreetype: Move PATH_SUFFIXES argument for more consistency
FindFreetype: Use lower-case name in call to FPHSA

Use 'find_package_handle_standard_args' because lower-case style is
now preferred.
FindFreetype: Indent with 2 spaces instead of 4

This is more consistent with style elsewhere.
cmake: Tolerate missing HELPSTRING on compiler change

Teach cmake::HandleDeleteCacheVariables to tolerate a missing HELPSTRING
(NULL pointer) when saving cache entries.  In the absence of other bugs
this should not be possible, but avoid the crash just in case.
cmCacheManager: Avoid cache entry self-assignment

Since commit bef93dc5 (Couple of changes: cache variables now have a map
of properties, 2002-09-11) the cmCacheManager::AddCacheDefinition method
accesses its map entry by reference.  However, the commit left the
original entry assignment at the end of the method.  With Apple Clang
5.1 and libc++ this self-assignment destroys the cache entry property
map.

Drop the self assignment.  Also drop the condition around the call to
UnwatchUnusedCli since it was a self-comparison that must always have
been true.
CTest: Improve Python coverage.py source file search algorithm

If the coverage.py source file is not found in the source directory, the
build directory is first searched before raising an error.

This is necessary because it is a valid workflow to build a Python
package from source, then install this package to a virtualenv that
lives in the build directory.  Tests will run against this deployed
package and therefore the covered source files will be found in a
subdirectory of the build directory, and not anywhere in the source
directory.
CTest: Fix Python coverage.py off-by-one error in results

The cobertura format uses line numbers indexed starting at 1, and CTest
uses a vector indexed starting at 0 to store them.
Add an "installed file" property scope

Teach set_property and get_property an "INSTALL" property type to be
associated with install-tree file paths.  Make the properties available
to CPack for use during packaging.  Add a "prop_inst" Sphinx domain
object type for documentation of such properties.
CPackWiX: Implement CPACK_NEVER_OVERWRITE and CPACK_PERMANENT properties
Merge topic 'fix-cache-self-assignment'

1cd37527 cmCacheManager: Avoid cache entry self-assignment
326d15a3 cmake: Tolerate missing HELPSTRING on compiler change
Merge topic 'GNUtoMS-vs-12'

668e571d GNUtoMS: Add support for VS 2013 (#14936)
Merge topic 'FindFreetype-updates'

58f7baab FindFreetype: Indent with 2 spaces instead of 4
444f8801 FindFreetype: Use lower-case name in call to FPHSA
836a28d5 FindFreetype: Move PATH_SUFFIXES argument for more consistency
4ad6dace FindFreetype: Add newlines to reduce code width
Merge topic 'cpack-properties'

d0b1d2a6 CPackWiX: Implement CPACK_NEVER_OVERWRITE and CPACK_PERMANENT properties
15a8af21 Add an "installed file" property scope
Merge topic 'fix-coverage-py'

deee7c42 CTest: Fix Python coverage.py off-by-one error in results
88b3dcb1 CTest: Improve Python coverage.py source file search algorithm