rt: rename nano_time() builtin to match time::precise_time_ns()

src/libstd/time.rs

@@ -5,7 +5,7 @@ Module: time
 #[abi = "cdecl"]
 native mod rustrt {
     fn get_time(&sec: u32, &usec: u32);
-    fn nano_time(&ns: u64);
+    fn precise_time_ns(&ns: u64);
 }
 
 /*
@@ -34,7 +34,7 @@ Function: precise_time_ns
 Returns the current value of a high-resolution performance counter
 in nanoseconds since an unspecified epoch.
 */
-fn precise_time_ns() -> u64 { let ns = 0u64; rustrt::nano_time(ns); ret ns; }
+fn precise_time_ns() -> u64 { let ns = 0u64; rustrt::precise_time_ns(ns); ns }
 
 /*
 Function: precise_time_s

src/rt/rust_builtin.cpp

@@ -420,7 +420,7 @@ get_time(uint32_t *sec, uint32_t *usec) {
 #endif
 
 extern "C" CDECL void
-nano_time(uint64_t *ns) {
+precise_time_ns(uint64_t *ns) {
     timer t;
     *ns = t.time_ns();
 }

src/rt/rustrt.def.in

@@ -13,10 +13,10 @@ get_port_id
 get_task_id
 get_time
 last_os_error
-nano_time
 new_port
 new_task
 port_recv
+precise_time_ns
 rust_port_select
 rand_free
 rand_new