Frame: remove platform specific unimplemented method

The generic version in Frame.cpp will work for us.
Add some unimplemented methods.

This allows to build WebKit in "shared core" mode, which is required to
run the test suite.
ResourceRequest: empty the URL on failure.

The ResourceLoader relies on that to know the load failed.
BWebFrame: initialize the history.

Make sure there is an empty item in the history before browsing start.
I'm not sure if that's the right solution, as other ports aren't calling
this method. Without this, we hit an assert when trying to load th first
page as it tries to move the "current" history item to "previous".
Tools/Scripts: minimal support for Haiku

Just prevent run-webkit-tests from complaining that the OS is unknown.
Add testing instructions to README.
MIME Type registry: remove useless assert.

There's nothing in this method that requires being in the main thread.
Cookie Jar: disable tracing

This is logging to stdout, which DumpRenderTree expects to have only the
dump. Should probably use WebKit logging facilities instead.
Get DumpRenderTree working as expected.

There are big differences on the implementation for this on each
platform. This borrows from EFL and BlackBerry ones:
- WebCore now provides a DumpRenderTreeClient interface, which
DumpRenderTree implements. This is registered at the BWebPage level.
- This interface is used both ways: WebCore can send (synchronous)
notifications to DRT, and DRT can access some WebCore internals.

DRT now actually injects the TestRunner into the JS world at the right
time so the tests can make use of it. This leads to some passing tests,
and still a lot of failures for various reasons. I'm going to complete
DRT support as needed to get more tests running.
More support for non-HTTP requests.

This is mainly used for file:, and soon for data:.