Compilation fixes for Linux/Gdk.

        * JavaScriptCore/kjs/interpreter.cpp: added include of signal.h
        * JavaScriptCore/kjs/ExecState.h: added missing class declaration 
        * JavaScriptCore/kjs/ExecState.cpp: case wrong on include of context.h 
        * JavaScriptCore/JavaScriptCoreSources.bkl: added Context.cpp and ExecState.cpp



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@15118 268f45cc-cd09-0410-ab3c-d52691b4dbfc