Fix build of curl on macosx.

Only build mupdf-x11-curl if the curl thirdparty library exists.
Bug 694516: Fix Android operation with passworded files.

Don't countPages until after we have a password.
Merge branch 'release' into 'master'.
pdfapp.c: Enable horizontal mouse scrolling.

This patch handles mouse buttons 6 and 7 and scrolls the page accordingly.
Implement continuous scrolling with 'j' and 'k'.
Implement "zoom to full extends" functionality.

The function pdfapp_autozoom zooms to fit the page to the window by computing
the aspect ratios of the page and the window and with that information either
zooming horizontally or vertically.
Maximize and auto-zoom when entering presentation.

When 'p' is pressed, the window is put into fullscreen-mode and the
pdfapp_autozoom is called.
Make automatic slide advancement configurable.

Pressing 'x' switches automatic slide advancement on or off.
Default is now off!
Make transition time -and type configurable.

Entering a number followed by 'x' sets the transition time in tenths of a
second.
Entering a number followed by 'X' sets the transition type.