Updated Doxygen markup in several .php files triggering warnings when mwdocgen.php is executed. Removed
obsolete settings MSCGEN_PATH and TCL_SUBST from Doxyfile. The former would generate a warning in 1.8.16
while TCL support was removed in 1.8.18. Since TCL_SUBST was blank anyway, it was removed prior to getting
to .18 in production. Increased DOT_GRAPH_MAX_NODES from 50 to 200 since Doxygen complained about it being
too low for API and Maintenance.
Bug: T248706
Change-Id: I9c67f0807d1b43089d351263d4f591dee5501f36
471d2371ab