WriteCompilerDetectionHeader: Add policy to remove module

Help/manual/cmake-compile-features.7.rst

Help/manual/cmake-modules.7.rst

Help/manual/cmake-policies.7.rst

Help/policy/CMP0120.rst

Help/release/dev/remove-WCDH-module.rst

Modules/WriteCompilerDetectionHeader.cmake

Source/cmIncludeCommand.cxx

Source/cmPolicies.h

...riteCompilerDetectionHeader/CMP0120-NEW-Direct-result.txt

...riteCompilerDetectionHeader/CMP0120-NEW-Direct-stderr.txt

...ake/WriteCompilerDetectionHeader/CMP0120-NEW-Direct.cmake

...CMake/WriteCompilerDetectionHeader/CMP0120-NEW-result.txt

...CMake/WriteCompilerDetectionHeader/CMP0120-NEW-stderr.txt

...s/RunCMake/WriteCompilerDetectionHeader/CMP0120-NEW.cmake

...ake/WriteCompilerDetectionHeader/CMP0120-OLD-Direct.cmake

...s/RunCMake/WriteCompilerDetectionHeader/CMP0120-OLD.cmake

...iteCompilerDetectionHeader/CMP0120-WARN-Direct-stderr.txt

...ke/WriteCompilerDetectionHeader/CMP0120-WARN-Direct.cmake

...Make/WriteCompilerDetectionHeader/CMP0120-WARN-stderr.txt

.../RunCMake/WriteCompilerDetectionHeader/CMP0120-WARN.cmake