FindBoost: Search next to MPI libraries for boost_mpi (#14739)

Some distributions place boost_mpi next to the MPI libraries against
which it was built instead of next to the other Boost libraries.  If
find_package(MPI) has already been run prior to find_package(Boost) then
MPI_CXX_LIBRARIES or MPI_C_LIBRARIES may be set to the location of the
MPI libraries.  Teach FindBoost.cmake to look there for boost_mpi and
boost_mpi_python after looking next to the other Boost libraries but
not consider the location to be Boost_LIBRARY_DIR.
OS X: Split Intel compiler information files

Create platform information modules Platform/Darwin-Intel-(C|CXX).cmake
and helper module Platform/Darwin-Intel.cmake.  Teach existing module
Platform/Darwin-Intel-Fortran.cmake to use the helper too.  Move
information from Platform/Darwin-icc.cmake into these files and drop
information already in Platform/Darwin.cmake to avoid duplication.
Sublime: Pass language and config properly
CMake Nightly Date Stamp
Add policy CMP0049 to avoid variable expansion in source lists
add_custom_command: Disallow use of SOURCE signatures.

Add CMP0050 to control this behavior.
Merge topic 'FindBoost-MPI-hints'

a22eeca3 FindBoost: Search next to MPI libraries for boost_mpi (#14739)
Merge topic 'osx-intel-info-split'

3693c63f OS X: Split Intel compiler information files
Merge topic 'cmake-devel-version-macro'

6ca6613a Export: Use the CMAKE_DEVEL_VERSION macro for build-export files.
Merge topic 'dev/fix-sublime-compile-flags'

2d9f93ab Sublime: Pass language and config properly
Merge topic 'backward-compatibility'

f2eee72f add_custom_command: Disallow use of SOURCE signatures.
c248a437 Add policy CMP0049 to avoid variable expansion in source lists
Help: Drop development topic notes to prepare release

Release versions do not have the development topic section of
the CMake Release Notes index page.
CMake 3.0.0-rc1 version update
Change version scheme to use only two components for feature levels

Historically CMake used three version components for the feature level.
We released new features while incrementing only the third version
component.  Since commit v2.8.2~105^2~4 (New version scheme to support
branchy workflow, 2010-04-23) we used the fourth version component for
bug-fix releases and the development date:

 <major>.<minor>.<patch>[.<tweak>][-rc<n>] = Release
 <major>.<minor>.<patch>.<date>[-<id>]     = Development

This solidified use of three components for the feature level, and was
necessary to continue releasing 2.x versions because:

* Some existing projects performed floating-point comparisons of
  ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION} to 2.x numbers
  so ``x`` could never be higher than 9.

* Version 2.9.<date> was used briefly in post-2.8.0 development in
  CVS prior to the transition to Git, so using it in releases may
  have caused confusion.

Now that we are moving to 3.x versions, these two restrictions go away.
Therefore we now change to use only two components for the feature
level and use the scheme:

 <major>.<minor>.<patch>[-rc<n>] = Release
 <major>.<minor>.<date>[-<id>]   = Development
WIP: Begin post-3.0 development

TODO: Rebase on final release and fix date