Add missing CMake commands for CMake lexer

[gnaggnoyil]

CMake has been adding new commands as time goes by and its development progreses. There are a few new commands available in the latest CMake release yet not recoginzed by current CMake lexer:

add_compile_definitions
add_link_options
cmake_language
cmake_parse_arguments
include_guard
target_compile_features
target_link_directories
target_link_options
target_precompile_headers
target_sources

This PR would allow CMake lexer to recoginze these commands correctly. For each command mentioned above, the earilest version that this command is available can be found in the document of latest CMake release.

[pyrmont]

@gnaggnoyil Thanks for adding these :) Merged in!