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

WPrefs.app/Appearance.c

@@ -402,6 +402,7 @@ static void dumpRImage(char *path, RImage * image)
 
 	fwrite(image->data, 1, image->width * image->height * channels, f);
 
+	fsync(fileno(f));
 	if (fclose(f) < 0) {
 		wsyserror(path);
 	}