Apply the make magic wand to pick an osdep-*.c file rather than using ifdefs.

Makefile

@@ -1,4 +1,4 @@
-# $Id: Makefile,v 1.126 2009-04-29 22:25:20 nicm Exp $
+# $Id: Makefile,v 1.127 2009-04-29 23:07:35 nicm Exp $
 
 .SUFFIXES: .c .o .y .h
 .PHONY: clean update-index.html upload-index.html
@@ -45,9 +45,7 @@ SRCS= tmux.c server.c server-msg.c server-fn.c buffer.c buffer-poll.c status.c \
       window-clock.c window-scroll.c window-more.c window-copy.c \
       window-choose.c \
       options.c options-cmd.c paste.c colour.c utf8.c clock.c \
-      tty.c tty-term.c tty-keys.c tty-write.c util.c names.c attributes.c \
-      osdep-unknown.c osdep-openbsd.c osdep-freebsd.c osdep-linux.c \
-      osdep-darwin.c osdep-netbsd.c
+      tty.c tty-term.c tty-keys.c tty-write.c util.c names.c attributes.c
 
 CC?= c
 INCDIRS+= -I. -I- -I/usr/local/include
@@ -96,6 +94,9 @@ LIBS+= -lcrypt
 CFLAGS+=-DNO_STRTONUM -DNO_QUEUE_H
 .endif
 
+OSDEP!= [ -f osdep-${OS:L}.c ] && echo ${OS:L} || echo unknown
+SRCS+= osdep-${OSDEP}.c
+
 OBJS= ${SRCS:S/.c/.o/:S/.y/.o/}
 
 DISTDIR= ${PROG}-${VERSION}