musl: define time_t as i64 type.

musl 1.1 maintenance has for all practical purposes ended.  Accordingly, there is
no point in supporting both 1.1 and 1.2 in the libc crate, so follow the
time_t type transition to 64-bit.

Author: kaniini

src/unix/linux_like/linux/musl/mod.rs

@@ -1,15 +1,6 @@
 pub type pthread_t = *mut ::c_void;
 pub type clock_t = c_long;
-#[cfg_attr(
-    not(feature = "rustc-dep-of-std"),
-    deprecated(
-        since = "0.2.80",
-        note = "This type is changed to 64-bit in musl 1.2.0, \
-                we'll follow that change in the future release. \
-                See #1848 for more info."
-    )
-)]
-pub type time_t = c_long;
+pub type time_t = i64;
 pub type suseconds_t = c_long;
 pub type ino_t = u64;
 pub type off_t = i64;