Make mkdtemp more portable

Taken from
https://github.com/gamma9mu/driftnet/commit/60659c3a7946c31e182655d6666977cdad3f1ea6

Conflicts:
	driftnet.c
Use pkgconfig for libpng

Conflicts:
	Makefile
Fix typo in button press_press-release
Allocate 64 instead of 34 bytes for path

Conflicts:
	src/display/display.c