use $(MAKE) instead make
support GNU conventions about INSTALL
support lower cases conventions on installation directory
sbin-y support

sbin-y works like bin-y but the installation is to <sbindir>=<prefix>/sbin instead <bindir>
only PREFIX, DATADIR and PKGLIBDIR could be set inside CONFIG
upme installation moves from bin to sbin
change support of directory value support

source code needs DATADIR and PKGLIBDIR. This definition should be inside config.h or pass to gcc options. Now it's only gcc options and it's programm dependent. scripts.mk doesn't need to manage definitions for the programm.
SRCTREE becomes srcdir as GNU conventions
directory definition must be exported at the first call of scripts.mk

if the main makefile defines other directories, the next calls of scripts.mk don"t retrieve the directories
the path finishes by /
the name of a library doesn't contain the path