In CMakeGraphVizOptions.cmake, allow the options GRAPHVIZ_GENERATE_PER_TARGET
and GRAPHVIZ_GENERATE_DEPENDERS to enable the generation of per target graphs
and subgraphs respectively. Both options are TRUE per default to maintain
current behavior.
Drop #end and #module. Convert #section to a subsection header.
Convert #variable to the cmake domain "variable" directive.
Convert #macro to the cmake domain "command" directive.
Perform minor formatting fixes in text near these changes.