Tests: Add generator platform support

Propagate CMAKE_GENERATOR_PLATFORM through the test hierarchy so that all
tests can build with the selected generator platform, if any.
enable_language: Initialize system-specific generator info only once

Call SetSystemName, SetGeneratorPlatform, and SetGeneratorToolset
exactly once after reading CMakeSystem.cmake, and not again on another
call to enable_language() or project().
Merge topic 'vs-generator-platform' into next

09c8ad99 enable_language: Initialize system-specific generator info only once
09ab207c Tests: Add generator platform support
Merge topic 'tolerate-lib-dir-symlink'

f99cc9c3 Tolerate symlinks during RPATH ordering (#13429)
Merge topic 'string-uuid-doc-fix'

e6ba52e8 StringUuid: Mark UPPER flag optional in sub-command synopsis
Merge topic 'FindIce-updates'

2131aedd FindIce: Respect Ice_FIND_QUIETLY when printing messages
d5047ca1 FindIce: Remove unneeded search path modification
Merge topic 'update-kwsys'

daab3b3b Merge branch 'upstream-kwsys' into update-kwsys
92b582a6 KWSys 2014-09-08 (fb77be5a)
Merge topic 'vs-generator-platform'

09c8ad99 enable_language: Initialize system-specific generator info only once
09ab207c Tests: Add generator platform support
6944997b ExternalProject: Propagate the generator platform
8d332091 CTest: Add options to set generator platform
b97736a2 VS: Implement CMAKE_GENERATOR_PLATFORM for VS >= 8
0f1f1271 CMake: Add CMAKE_GENERATOR_PLATFORM option
4f7d0c42 Help: Document CMAKE_VS_PLATFORM_NAME variable
68d4280a VS: Refactor internal default platform name selection
ad2a4776 cmGlobalVisualStudio10Generator: Re-order some methods
03b7b6cd cmGlobalGenerator: Call SetGeneratorToolset even for empty toolset
Merge branch 'master' into next