Added a nanosecond timer to time.rs, support for some floating point casts, and a commandline-driven mode for pfib.rs

src/lib/time.rs

@@ -2,6 +2,7 @@
 
 native "rust" mod rustrt {
     fn get_time(&mutable u32 sec, &mutable u32 usec);
+    fn nano_time(&mutable u64 ns);
 }
 
 type timeval = rec(u32 sec, u32 usec);
@@ -11,4 +12,14 @@ fn get_time() -> timeval {
     auto usec = 0u32;
     rustrt::get_time(sec, usec);
     ret rec(sec=sec, usec=usec);
-}
+}
+
+fn precise_time_ns() -> u64 {
+    auto ns = 0u64;
+    rustrt::nano_time(ns);
+    ret ns;
+}
+
+fn precise_time_s() -> float {
+    ret (precise_time_ns() as float) / 1000000000.;
+}