The Makefiles should put binaries in $(EXEC_PREFIX) and
architecture-independent files in $(PREFIX). Also a user may have a
prefixed- pkg-config, as in the case of cross compiling on Exherbo
Linux, so respect the well-accepted $(PKG_CONFIG) variable for this
purpose.
This removes our last dependency on Xlib! :)
(Okay, an Xlib dependency still comes in through other libraries that we
link against, but it’s not us. Our code is simpler by this change and
uses one less connection to X11.)
CPPFLGES, CFLAGS and LDFLAGS should be user variables
We now provide default flags but use I3_*FLAGS flags for our own needed
flags
Also reoder lib flags a bit
Thomas Anderson