refactor makefile

Conflicts:
	makefile
make: Fixes for FreeBSD.
Added install target to makefile
make: Follow INSTALL_* convention.
make: Added support for prefix, bindir, etc.
Renamed makefile -> Makefile.

Most people appear to be using "Makefile" instead of "makefile" and it's
somewhat recommended by GNU:

http://www.gnu.org/software/make/manual/html_node/Makefile-Names.html
make: Added target "dist".
make: Fixes for OpenBSD.

OpenBSD's "install" does not know "-D". I figured the easiest way is
simply a "mkdir -p". I know that's not recommended. See my comment,
though:

	Note: We only support GNU, OpenBSD and FreeBSD right now and all
	of them know "mkdir -p".
Don't use gtk_widget_set_size_request().

That function enforces a minimum size. It's better to use
gtk_window_set_default_size() on the windows.
Fixed: Crash on documents with not enough pages.

Background caching (idleFillCaches()) triggers pre-rendering of the
previous and next page of each viewport. Unfortunately,
getRenderedPixbuf() did not correctly check whether the requested page
is valid. On documents which contain exactly one page this resulted in a
crash of pdfpres.

Fix: Correctly check whether mypage_i is a valid page number.
Update GtkFrame labels at the appropriate place.

Updating them in updatePortPixbuf() is wrong in two ways: a) They don't
need to be updated when the *size* of the ports changes, b) they may
re-emit a size-allocate signal which can cause freezes on Kubuntu (see
issue #42).
Split: onResize + onExpose.

We must not cause widgets to change their size as long as we're inside
of onResize().
replace dieOnNull() with g_assert()
call gtk_widget_add_events only once per window
advance slides on scrolling
Merge pull request #44 from t-8ch/g_assert

replace dieOnNull() with g_assert().
Merge pull request #43 from t-8ch/scrolling

Scrolling (browsing slides using the mouse wheel).
Merge branch 'master' into gtk3