Switch file ops to stdio

- Does away with the O_BINARY abomination
- as a byproduct, plugs an fd leak in wcolorpanel.c:fetchFile()
- sprinkle some fsync()s to files that have been written to (this
  needs to be done everywhere)

+ fix brown paper bag thinko in configure.ac

configure.ac

@@ -41,8 +41,7 @@ dnl Platform-specific Makefile setup
 dnl ================================
 
 case "${host}" in
-	*-*-cygwin*)
-	*-*-linux*)
+	*-*-linux*|*-*-cygwin*)
 		WM_OSDEP="linux"
 	;;
 	*-*-freebsd*)