Turns out, some packages like serdisplib actually use libusb-config.
Fix the paths in it so that they can work properly. Method taken from
libpng.
Signed-off-by: Rosen Penev <rosenp@gmail.com>
Upstream moved to GitHub. Adjust accordingly.
Cleaned up Makefile for consistency between packages.
Made InstallDev section more explicit.
Used ABI_VERSION in install section.
Signed-off-by: Rosen Penev <rosenp@gmail.com>