Enable the extraction of static function documentation.

doxygen/math.doxy

@@ -9,7 +9,7 @@ OUTPUT_DIRECTORY       = .
 OUTPUT_LANGUAGE        = English
 EXTRACT_ALL            = YES
 EXTRACT_PRIVATE        = NO
-EXTRACT_STATIC         = NO
+EXTRACT_STATIC         = YES
 EXTRACT_LOCAL_CLASSES  = YES
 HIDE_UNDOC_MEMBERS     = NO
 HIDE_UNDOC_CLASSES     = NO