Add iterator safety check in DoxygenParser::parse

If the code called by DoxygenParser::parse does not behave correctly,
it may move the iterator m_tokenListIt past the value endParsingIndex.
This was not caught by the previous checks and could lead to
dereferencing an invalid m_tokenListIt iterator value (and segfault).
This is now protected against by using a less than check in the while
loop instead of not equals.  A warning is also printed if
endParsingIndex is exceeded.

Source/Include/swigwarn.h

@@ -221,6 +221,7 @@
 #define WARN_DOXYGEN_HTML_ERROR               563
 #define WARN_DOXYGEN_COMMAND_ERROR            564
 #define WARN_DOXYGEN_UNKNOWN_CHARACTER        565
+#define WARN_DOXYGEN_UNEXPECTED_ITERATOR_VALUE  566
 
 /* -- Reserved (600-799) -- */