Make it a build error to put invalid C++ symbol names in WebCore.exp.in
https://bugs.webkit.org/show_bug.cgi?id=115958

Reviewed by Andreas Kling.

While invalid C++ symbols will eventually show up as a link error since the symbol won't be found,
this makes it easier to catch invalid symbols inside of #ifdefs.

* make-export-file-generator:
Try to demangle C++ symbols before printing them.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@149932 268f45cc-cd09-0410-ab3c-d52691b4dbfc