Tests/Preprocess: Remove unnecessary VS version tests

Since commit v2.8.12~436^2 (VS 10: Escape ; as %3B in preprocessor
definitions, 2013-04-11) the Tests/Preprocessor/CMakeLists.txt file no
longer uses the PP_VS1XX values, so stop setting them.
VS14: Add Visual Studio 14 generator (#14982)

Call the generator "Visual Studio 14" without any year because this
version of VS does not provide a year in the product name.

Copy cmGlobalVisualStudio12Generator to cmGlobalVisualStudio14Generator
and update version numbers accordingly.  Add the VS14 enumeration value.
Teach the platform module Windows-MSVC to set MSVC14 and document the
variable.  Teach module InstallRequiredSystemLibraries to look for the VS
14 runtime libraries.

Teach tests CheckCompilerRelatedVariables, VSExternalInclude, and
RunCMake.GeneratorToolset to treat VS 14 as they do VS 10, 11, and 12.

Co-Author: Pawel Stopinski <diokhan@go2.pl>
VS14: Generate flag tables from MSBuild v140 tool files

Run cmparseMSBuildXML.py on cl.xml, lib.xml, and link.xml to generate
our flag tables:

 python cmparseMSBuildXML.py -x ".../MSBuild/Microsoft.Cpp/v4.0/V140/1033/cl.xml" > cmVS14CLFlagTable.h
 python cmparseMSBuildXML.py -x ".../MSBuild/Microsoft.Cpp/v4.0/V140/1033/lib.xml" > cmVS14LibFlagTable.h
 python cmparseMSBuildXML.py -x ".../MSBuild/Microsoft.Cpp/v4.0/V140/1033/link.xml" > cmVS14LinkFlagTable.h

Fix up the declaration names at the top of each file.  Finally, teach
cmVisualStudio10TargetGenerator to select the version of the table
matching the version of VS.

Co-Author: Pawel Stopinski <diokhan@go2.pl>
VS14: Fix Cl and Link flag tables as previous versions

Apply the flag table fixes from:

 commit 9c7f234c (VS: Fix /MANIFESTUAC:NO linker option mapping, 2014-05-07)
 commit e8633e66 (VS: Fix /analyze:log flag mapping, 2014-04-01)
 commit f2caf795 (VS: Fix /MAP:mapfile flag mapping, 2013-07-09)

to the VS 14 flag tables.
FindBoost: Add -vc140 mangling for VS 14

Co-Author: Pawel Stopinski <diokhan@go2.pl>
Tests: Simplify LoadCommand tests

Drop out-of-place coverage of CheckFunctionExists module.  The "printf"
symbol is not available on VS 14 without including the <stdio.h> header
to get a definition.
Merge topic 'vs14-generator' into next

5c105140 Tests: Simplify LoadCommand tests
b1cbd577 FindBoost: Add -vc140 mangling for VS 14
bdc7d9c8 VS14: Fix Cl and Link flag tables as previous versions
d96b3f68 VS14: Generate flag tables from MSBuild v140 tool files
65624c39 VS14: Add Visual Studio 14 generator (#14982)
8635ac23 Tests/Preprocess: Remove unnecessary VS version tests