Merge branch 'ipo-per-lang' into release-3.9

Modules/CheckIPOSupported.cmake

Modules/Compiler/Clang.cmake

Modules/Compiler/GNU.cmake

Modules/Compiler/QCC.cmake

Modules/Platform/Linux-Intel.cmake

Source/cmGeneratorTarget.cxx

Source/cmGeneratorTarget.h

Source/cmGlobalXCodeGenerator.cxx

Source/cmLocalGenerator.cxx

Source/cmLocalVisualStudio7Generator.cxx

Source/cmMakefileLibraryTargetGenerator.cxx

Source/cmNinjaNormalTargetGenerator.cxx

Source/cmVisualStudio10TargetGenerator.cxx

Tests/RunCMake/CMP0069/CMP0069-NEW-cmake.cmake

Tests/RunCMake/CMP0069/CMP0069-NEW-compiler.cmake

Tests/RunCMake/CMP0069/CMP0069-NEW-generator.cmake

Tests/RunCMake/CMP0069/CMP0069-WARN.cmake

...CMake/CheckIPOSupported/not-supported-by-cmake-stderr.txt

...s/RunCMake/CheckIPOSupported/not-supported-by-cmake.cmake

...ke/CheckIPOSupported/not-supported-by-compiler-stderr.txt