Update srcSAX Submodule Commit #47

The current commit of srcSAX being used (d4e394e) has a protected member field in src/cpp/srcSAXHandler.hpp:51 called srcml_element_stack. The current commit on master has since renamed it to just element_stack, which is the name srcDispatch.hpp uses. This causes a compilation error if attempting to compile srcDispatch without the latest updating to the latest commit of srcSAX or manually renaming the variable in the local version.