try_compile: Add signature to allow multiple SOURCES

Extend the signature

 try_compile(RESULT_VAR <bindir> <srcfile> ...)

to allow multiple sources as

 try_compile(RESULT_VAR <bindir> SOURCES <srcfile>... ...)

Process the sources to generate a CMakeLists.txt that enables all needed
languages.

Teach the TryCompile test to try cases with two sources of the same
language and of mixed languages.  Teach RunCMake.try_compile to cover
error cases for the signature.
VS: Add support for .NET target framework version

Teach CMake to generate the TargetFrameworkVersion XML node as
documented at

 http://msdn.microsoft.com/en-us/library/vstudio/ff770576.aspx

from target property VS_DOTNET_TARGET_FRAMEWORK_VERSION.
Split cmBootstrapCommands.cxx into two sources

The single translation unit has grown too large for some compilers.
Split it into cmBootstrapCommands1.cxx and cmBootstrapCommands2.cxx.
Document CMAKE_INSTALL_PREFIX in CMAKE_SYSTEM_PREFIX_PATH

Add documentation to both variables to indicate that the install prefix
is also searched.
UseJava.cmake: document add_jar compat shim

Document the logic that parses for backward compatibility the old
variables that were used to control add_jar prior to named argument
support. In particular, document that the reason this logic exists is
for backward compatibility, and that new features do not need to add to
it.
Add cmake_host_system_information command

Expose the internal system information API to the CMake language.  For
example, it is useful to see how much memory the system has available to
estimate an upper limit of tests that can run in parallel.
cmake: Document "-E tar" support for .zip (#14225)

Through use of libarchive internally we support .zip files as well as
.tar format.  The ExternalProject module makes use of this feature.
Document support officially.
Merge topic 'vs-TargetFrameworkVersion'

cfe6300 VS: Add support for .NET target framework version
Merge topic 'split-command-sources'

b9f4383 Split cmBootstrapCommands.cxx into two sources
Merge topic 'doc-search-install-prefix'

a0b37d7 Document CMAKE_INSTALL_PREFIX in CMAKE_SYSTEM_PREFIX_PATH
Merge topic 'document-add_jar-compat-shims'

b41771d UseJava.cmake: document add_jar compat shim
Merge topic 'add-try_compile-options'

482f112 try_compile: Add signature to allow multiple SOURCES
Merge topic 'add-cmake_host_system_information-command'

bb71a3a Add cmake_host_system_information command
Merge topic 'doc-E-tar-zip'

ae06f80 cmake: Document "-E tar" support for .zip (#14225)