Now that set_property and set_target_properties support ALIAS targets,
we need to extend support to all the target_* type commands that modify
target properties.
Relaxes target_compile_definitions, target_compile_features,
target_compile_options, target_include_directories,
target_link_directories, target_link_libraries, target_link_options,
target_precompile_headers, and target_sources to now accept ALIAS
targets. These commands set properties on the target which the alias
references.
