Discussed with and rubber-stamped by Lars.

        Fix the build system for the Qt port.

        Recent JavaScriptCore changes require the addition of JavaScriptCore/API to the
        include search path. With a build process that combines JavaScriptCore and
        WebCore in one build process/Makefile the existance of
        JavaScriptCore/API/Node.h and WebCore/dom/Node.h causes include conflicts.

        This commit solves this by introducing a separate build of JavaScriptCore into
        a static library.

        As a result of the split-up a race-condition due to broken dependencies of
        regular source files to header files of generated sources showed up very
        frequently when doing parallel builds (which the buildbot does). This commit at
        the same time tries to address the dependency problem by making the
        addExtraCompiler() function also generate a pseudo extra compiler that
        represents the header file output, so that qmake is aware of the creation of
        the header file for dependency calculation.

        At the same time I removed a lot of cruft from the pro files to ease maintenance.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@35335 268f45cc-cd09-0410-ab3c-d52691b4dbfc