Fix doxyfile to include JBMC documentation

Also include unit test utilities in the documentation.

Author: thk123

src/doxyfile

@@ -771,7 +771,7 @@ WARN_LOGFILE           =
 # spaces. See also FILE_PATTERNS and EXTENSION_MAPPING
 # Note: If this tag is empty the current directory is searched.
 
-INPUT                  = . ../doc
+INPUT                  = . ../doc ../jbmc/src ../unit/testing-utils ../jbmc/unit/java-testing-utils
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses