Add clock_settime()

See http://www.catb.org/esr/time-programming/#_clock_gettime_2_clock_settime_2_clock_getres_2

src/unix/bsd/freebsdlike/dragonfly/mod.rs

@@ -374,6 +374,7 @@ extern {
                     -> ::c_int;
     pub fn clock_getres(clk_id: clockid_t, tp: *mut ::timespec) -> ::c_int;
     pub fn clock_gettime(clk_id: clockid_t, tp: *mut ::timespec) -> ::c_int;
+    pub fn clock_settime(clk_id: clockid_t, tp: *const ::timespec) -> ::c_int;
 
     pub fn setutxdb(_type: ::c_uint, file: *mut ::c_char) -> ::c_int;
 

src/unix/bsd/freebsdlike/freebsd/mod.rs

@@ -364,6 +364,7 @@ extern {
 
     pub fn clock_getres(clk_id: clockid_t, tp: *mut ::timespec) -> ::c_int;
     pub fn clock_gettime(clk_id: clockid_t, tp: *mut ::timespec) -> ::c_int;
+    pub fn clock_settime(clk_id: clockid_t, tp: *const ::timespec) -> ::c_int;
 
     pub fn posix_fallocate(fd: ::c_int, offset: ::off_t,
                            len: ::off_t) -> ::c_int;

src/unix/bsd/netbsdlike/mod.rs

@@ -472,6 +472,8 @@ extern {
     pub fn clock_getres(clk_id: clockid_t, tp: *mut ::timespec) -> ::c_int;
     #[cfg_attr(target_os = "netbsd", link_name = "__clock_gettime50")]
     pub fn clock_gettime(clk_id: clockid_t, tp: *mut ::timespec) -> ::c_int;
+    #[cfg_attr(target_os = "netbsd", link_name = "__clock_settime50")]
+    pub fn clock_settime(clk_id: clockid_t, tp: *const ::timespec) -> ::c_int;
     pub fn __errno() -> *mut ::c_int;
     pub fn shm_open(name: *const ::c_char, oflag: ::c_int, mode: ::mode_t)
                     -> ::c_int;

src/unix/haiku/mod.rs

@@ -712,6 +712,7 @@ f! {
 
 extern {
     pub fn clock_gettime(clk_id: ::c_int, tp: *mut ::timespec) -> ::c_int;
+    pub fn clock_settime(clk_id: ::c_int, tp: *const ::timespec) -> ::c_int;
     pub fn pthread_attr_getguardsize(attr: *const ::pthread_attr_t,
                                      guardsize: *mut ::size_t) -> ::c_int;
     pub fn pthread_attr_getstack(attr: *const ::pthread_attr_t,

src/unix/notbsd/mod.rs

@@ -725,6 +725,7 @@ extern {
                            flags: ::c_int,
                            rqtp: *const ::timespec,
                            rmtp:  *mut ::timespec) -> ::c_int;
+    pub fn clock_settime(clk_id: clockid_t, tp: *const ::timespec) -> ::c_int;
     pub fn prctl(option: ::c_int, ...) -> ::c_int;
     pub fn pthread_getattr_np(native: ::pthread_t,
                               attr: *mut ::pthread_attr_t) -> ::c_int;

src/unix/solaris/mod.rs

@@ -979,6 +979,7 @@ extern {
                            flags: ::c_int,
                            rqtp: *const ::timespec,
                            rmtp:  *mut ::timespec) -> ::c_int;
+    pub fn clock_settime(clk_id: clockid_t, tp: *const ::timespec) -> ::c_int;
     pub fn getnameinfo(sa: *const ::sockaddr,
                        salen: ::socklen_t,
                        host: *mut ::c_char,