rustc: Add 'target_family' to default configuration

Author: brson

src/rustc/driver/driver.rs

@@ -50,6 +50,7 @@ fn default_configuration(sess: session, argv0: str, input: input) ->
 
     ret [ // Target bindings.
          mk("target_os", os::sysname()),
+         mk("target_family", os::family()),
          mk("target_arch", arch),
          mk("target_libc", libc),
          // Build bindings.

src/test/run-pass/cfg-target-family.rs

@@ -0,0 +1,7 @@
+#[cfg(target_family = "windows")]
+fn main() {
+}
+
+#[cfg(target_family = "unix")]
+fn main() {
+}