Help: Add introduction section to cmake-policies manual

Explain the concept behind policies.
cmExtraEclipseCDT4Generator: Replace RunCommand with RunSingleCommand

Avoid use of the old cmSystemTools::RunCommand by using RunSingleCommand
instead.
CTest: prioritize tests by their depth in the dependency graph
CMake Nightly Date Stamp
CTest: consider previously failed tests before all others
CTest: perform cycle test early
VS 6: Do not try Intel Fortran .vfproj file with msdev

Teach CMakeDetermineCompilerId to skip trying to build a .vfproj
file for Intel Fortran under Visual Studio 6.  The msdev command-line
build produces a popup error dialog that hangs the configuration.
Cygwin: Avoid legacy warnings in RunCMake.CMP0026 test

Set the minimum required version of CMake high enough to avoid the
warning for CMAKE_LEGACY_CYGWIN_WIN32.  The warning appears on stderr
and breaks the expected output matching.
cmake: Drop "cmake -E comspec" Win9x helper

Since we dropped Win9x support there is no need for this helper.
exec_program: Re-implement using KWSys Process

Drop use of cmSystemTools::RunCommand.  It used popen on UNIX
(equivalent to /bin/sh -c "$command") and direct CreateProcess calls on
Windows.  Implement equivalent behavior using the KWSys Process library.
Copy windows shortpath conversion logic from cmSystemTools::RunCommand.
cmSystemTools: Drop old RunCommand method

All calls to this method have been replaced by newer infrastructure.
Remove it and the supporting cmWin32ProcessExecution class.
CMake Nightly Date Stamp
cmCoreTryCompile: Fix typo in comments.

Add 'S' to match actual variable names.
Merge topic 'vs-intel-compiler'

1b7117a VS 6: Do not try Intel Fortran .vfproj file with msdev
Merge topic 'target-LOCATION-policy'

abfebef Cygwin: Avoid legacy warnings in RunCMake.CMP0026 test
CMake Nightly Date Stamp
Merge topic 'cmake-syntax-updates'

daa0f6f Add Lua-style long brackets and long comments to CMake language
a8c6523 cmListFileLexer: Convert CRLF -> LF newlines explicitly
dbd9333 cmListFileLexer: Allow a leading UTF-8 Byte-Order-Mark (#11137)
5645783 cmListFileLexer: Allow command names with one letter (#14181)
Merge topic 'vs12-parallel-cl-FS'

216afc8 MSVC: Add /FS flag for cl >= 18 to allow parallel compilation (#14492)
Merge topic 'policies-generic-docs'

6d50d01 Help: Add introduction section to cmake-policies manual
Merge topic 'remove-old-process-execution'

765d783 cmSystemTools: Drop old RunCommand method
52b80b2 exec_program: Re-implement using KWSys Process
c076476 cmake: Drop "cmake -E comspec" Win9x helper
f551135 cmExtraEclipseCDT4Generator: Replace RunCommand with RunSingleCommand