Update doxygen version to 2.0.3 as in init.h

(cherry picked from commit 59fba75cd8f94343d2ac5cafe6a79578fde7b994)

doc/doxygen/lwip.Doxyfile

@@ -38,7 +38,7 @@ PROJECT_NAME           = "lwIP"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = "2.0.2"
+PROJECT_NUMBER         = "2.0.3"
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a