iproute2 - Fix up and simplify variables pointing to install directories

Define where is the are located the iproute2 config files.
Get rid of trailing slashes for paths in several file.

Signed-off-by: Christoph J. Thompson <cjsthompson@gmail.com>
diff --git a/Makefile b/Makefile
index 1f6c8bf..c107955 100644
--- a/Makefile
+++ b/Makefile
@@ -1,10 +1,11 @@
-DESTDIR=/usr/
 ROOTDIR=$(DESTDIR)
-LIBDIR=/usr/lib/
+PREFIX=/usr
+LIBDIR=$(PREFIX)/lib
 SBINDIR=/sbin
 CONFDIR=/etc/iproute2
-DOCDIR=/share/doc/iproute2
-MANDIR=/share/man
+DATADIR=$(PREFIX)/share
+DOCDIR=$(DATADIR)/doc/iproute2
+MANDIR=$(DATADIR)/man
 ARPDDIR=/var/lib/arpd
 
 # Path to db_185.h include
@@ -17,6 +18,8 @@
 DEFINES+= -DNO_SHARED_LIBS
 endif
 
+DEFINES+=-DCONFDIR=\"$(CONFDIR)\"
+
 #options if you have a bind>=4.9.4 libresolv (or, maybe, glibc)
 LDLIBS=-lresolv
 ADDLIB=