ExternalProject: Clarify SVN_REVISION format in docs (#15081)

Show the explicit '-r' that is required.
cmIDEOptions: Add an AppendFlag overload to append multiple values
cmIDEOptions: Add HasFlag method to test if a flag is set
VS: Refactor include directory slash conversion

Convert each include directory to windows slashes once instead of
repeating it each time they are written out to the project file.
VS: Refactor include directory generation in .vcxproj files

Use the cmVisualStudioGeneratorOptions flag map to add the
AdditionalIncludeDirectories element to the project file.
Move appending of %(AdditionalIncludeDirectories) to the
locations that populate the flag vectors instead of where
they are written out.
cmListFileLexer: Fix lexing of single '[' character (#15092)

The lexer changes in commit v3.0.0-rc1~495^2 (Add Lua-style long
brackets and long comments to CMake language, 2013-08-06) accidentally
left out matching '[' as a single character in an unquoted argument.
Add a lexer rule to match it and extend the RunCMake.Syntax test to
cover this case.
Merge branch 'fix-lexer-open-square' into release
Check*: Add compatibility hack for old VXL code

The cleanup in commit 4f2fcce4 (Check*: Allow result variables to
contain regex special characters, 2014-07-31) broke old VXL code that
abuses the old "if(MATCHES)" implementation by using

  SET( ${VARIABLE} ${VARIABLE} )

to reset a check result variable.  Add a compatibility hack to the
CheckFunctionExists, CheckIncludeFileCXX, and CheckSymbolExists modules
to re-run their checks when the result variable is set to its own name.
Use STREQUAL instead of MATCHES so that special characters still work.
FindOpenMP: Add support for Fortran (#14656)
Merge topic 'ExternalProject-doc-SVN_REVISION-format'

b26faaf1 ExternalProject: Clarify SVN_REVISION format in docs (#15081)
Merge topic 'vs-refactor-includes'

5fcb42ab VS: Refactor include directory generation in .vcxproj files
8e026aa7 VS: Refactor include directory slash conversion
9633d112 cmIDEOptions: Add HasFlag method to test if a flag is set
84100102 cmIDEOptions: Add an AppendFlag overload to append multiple values
Merge topic 'fix-lexer-open-square'

02b3cba9 cmListFileLexer: Fix lexing of single '[' character (#15092)
Merge topic 'fix-check-module-DEFINED-tests'

4ffec8f6 Check*: Add compatibility hack for old VXL code
Merge topic 'FindOpenMP-add-Fortran-support'

d0678408 FindOpenMP: Add support for Fortran (#14656)
Merge branch 'release'