Issue #2170519 by longwave, kim.pepper: Fix comments in TestBase to add missing class names
Issue #2175765 by alexpott, Gábor Hojtsy: Fix comment in system_theme_default() to not refer to obsolete function
Issue #2174569 by pjonckiere, dawehner: Fix class name references in TestBase docs
Issue #2177175 by Xano, longwave: Remove PHP module from MAINTAINERS.txt
Issue #2176085 by jessebeach, valthebald: Make code comment in entity_get_render_display() clearer