ConfirmBox and InfoMessage are default to be modal.
Now returning to filamanager after highlighting a PDF page
the confirmbox asking users to save the document will not be hidden by
the filamanager window.
And it's tested on Kindle that #791 is already been solved probably by
out refacorting of MuPDF backend.
colors were a mixture of 4bpp integers (0=white, 15=black) and
fractional blackness levels (0=white, 1.0=black) before. This is
now unified to use the color specification of the Blitbuffer API.
This should finish the work to make all globals to local variables.
That allows LuaJIT to properly compile things by interning the
references to the relevant parts (rather than looking up globals
all the time which stops a trace).