Document ENV syntax as a "variable" (#14245)

Although "ENV" is not a special variable itself, use it to document
the $ENV{VAR} syntax.
KWSys 2013-06-24 (3d1d4e7c)

Extract upstream KWSys using the following shell commands.

$ git archive --prefix=upstream-kwsys/ 3d1d4e7c | tar x
$ git shortlog --no-merges --abbrev=8 --format='%h %s' d79a792e..3d1d4e7c
Cory Quammen (1):
      3d1d4e7c SystemTools: MakeDirectory() reports failure if path is file

Change-Id: I080ed62630304c63c65efaf4be08198a6411ae48
Merge branch 'upstream-kwsys' into update-kwsys
Embarcadero: Use response files only for includes, objects, and libs

Leave other flags directly in the Makefile command lines and outside
any special inline response file syntax.  Otherwise Borland does
not support flags with quotes in response files.
Escape target flags taken from COMPILE_OPTIONS

Factor appending of individual flags out into an AppendFlagEscape method
in cmLocalGenerator and teach it to use EscapeForShell.  Update all
COMPILE_OPTIONS handling to use AppendFlagEscape.

Override the method in the Xcode generator to use its custom escape
implementation.

Teach the CompileOptions test to add an option that requires escaping
everywhere instead of just with the GNU tools.
Refactor target COMPILE_OPTIONS and COMPILE_FLAGS handling

Replace the cmLocalGenerator GetCompileOptions method with an
AddCompileOptions method since all call sites of the former simply
append the result to a flags string anyway.

Add a "lang" argument to AddCompileOptions and move the
CMAKE_<LANG>_FLAGS_REGEX filter into it.  Move the call sites in each
generator to a location that has both the language and configuration
available.  In the Makefile generator this also moves the flags from
build.make to flags.make where they belong.
Merge topic 'doc-ENV-syntax'

c293e05 Document ENV syntax as a "variable" (#14245)
Merge topic 'update-kwsys'

063617c Merge branch 'upstream-kwsys' into update-kwsys
045fc84 KWSys 2013-06-24 (3d1d4e7c)
Merge topic 'refactor-compile-options'

d221eac Refactor target COMPILE_OPTIONS and COMPILE_FLAGS handling
b6385ca Escape target flags taken from COMPILE_OPTIONS
0c9cc9a Embarcadero: Use response files only for includes, objects, and libs