While a process is running, it is possible for other processes such as
NTP to alter the system clock in large jumps.

To make the measurement of how long a process has taken to run
impervious to such large jumps it is helpful to use a monotonic clock.
This is a clock that takes an arbitrary starting point that does not
change.

clock_gettime() is a POSIX method that implements this clock. This is
not available on all platforms, so this commit adds a check for its
presence. If the monotonic timer is available, use that in
kwsysProcessTimeGetCurrent(), otherwise falls back to previous
non-monotonic behaviour.

Run the `clang-format.bash` script to update all our C and C++ code to a new
style defined by `.clang-format`.  Use `clang-format` version 3.8.

* If you reached this commit for a line in `git blame`, re-run the blame
  operation starting at the parent of this commit to see older history
  for the content.

* See the parent commit for instructions to rebase a change across this
  style transition commit.

Change-Id: Ie3aedc03bfe5c3999d4a077fafb8c6f3bbffc5c5

Per-source copyright/license notice headers that spell out copyright holder
names and years are hard to maintain and often out-of-date or plain wrong.
Precise contributor information is already maintained automatically by the
version control tool.  Ultimately it is the receiver of a file who is
responsible for determining its licensing status, and per-source notices are
merely a convenience.  Therefore it is simpler and more accurate for
each source to have a generic notice of the license name and references to
more detailed information on copyright holders and full license terms.

Our `Copyright.txt` file now contains a list of Contributors whose names
appeared source-level copyright notices.  It also references version control
history for more precise information.  Therefore we no longer need to spell
out the list of Contributors in each source file notice.

Replace KWSys per-source copyright/license notice headers with a short
description of the license and links to `Copyright.txt` and online
information available from "https://cmake.org/licensing#kwsys".

Run the `filter-notices.bash` script to perform the replacements mechanically.
Manually fix up the shebang line in one file.

Change-Id: I8497f7c868664dcf54a8608ab302ad93c860b334

The FundamentalType header needs to know type sizes at preprocessing
time.  This commit teaches it to avoid using CHECK_TYPE_SIZE because the
macro does not work for types whose size varies across architectuers in
Mac OS X universal binaries.  Fortunately the Mac compilers provide just
enough information to detect the needed type sizes during preprocessing.

We now use preprocessor macros instead of configuration tests whenever
they are available.  As a side effect this reduces the number of
try-compiles needed with GCC.

See issue #9913.

This converts the KWSys license to a pure 3-clause OSI-approved BSD
License.  We drop the previous license clause requiring modified
versions to be plainly marked.  We also update the KWSys copyright to
cover the full development time range.

ENH: Adding tests KWSYS_C_HAS_PTRDIFF_T and KWSYS_C_HAS_SSIZE_T to help ProcessUNIX.c build everywhere without warnings.

ENH: Renamed kwsysPlatformCxxTests to kwsysPlatformTests and generalized it for multiple language tests (C and CXX).