This cleans up this header and moves the functionality into more
useful places while reducing the include complexity but only pulling
in whats required.
Update the API which allows frontends to acquire the page features
(images, link urls or form elements) present at the given coordinates
within a browser window.
By making this an explicit browser_window API and using the browser.h
header for the associated data structure with a more appropriate API
naming the usage is much more obvious and contained.
Additionally the link url is now passed around as a nsurl stopping it
being converted from nsurl to text and back again several times.
This removes the global PDF_Password interface that had completely
bitrotted and moves it into the standard misc operation table with a
sensible defualt implementation.
This also cleans up and fixes the gtk frontend implementation of the
pdf password callback so it compiles.
Finally this moves the implementation to a sensible place alongside
the other exporters reducing target makefile complexity futher.
The die() API for abnormal termination does not belong within the core
of netsurf and instead errors are propogated back to the callers.
This is the final part of this change and the API is now only used within
some parts of the frontends
Returning an error instead of simply calling die allows more robust
error handling. Secondly initialisation may continue even if the
messages have not been loaded which is more friendly than simply
dropping dead with no communication to the user.
The netsurf.h header should *only* contain the registration, core
initialisation and finalisation methods. Version information is best
placed in its own header.
Also remove any unneeded inclusion of this header limiting it to
solely the places the relevant API is required.
