Auto merge of #3146 - lcheylus:openbsd, r=JohnTitor

Add OpenBSD CLOCK_* constants

To compile [`wasmer-wasi`](https://github.com/wasmerio/wasmer/tree/master/lib/wasi) crate (part of Wasmer) on OpenBSD, I need to add CLOCK_* constants from `/usr/include/sys_time.h` file.

- Add CLOCK_* constants in `src/unix/bsd/netbsdlike/openbsd/mod.rs`
- Update `libc-test/semver/openbsd.txt` accordingly

cc `@semarie`

libc-test/semver/openbsd.txt

@@ -98,6 +98,10 @@ CLD_EXITED
 CLD_KILLED
 CLD_STOPPED
 CLD_TRAPPED
+CLOCK_BOOTTIME
+CLOCK_PROCESS_CPUTIME_ID
+CLOCK_THREAD_CPUTIME_ID
+CLOCK_UPTIME
 CMSG_DATA
 CMSG_FIRSTHDR
 CMSG_LEN

src/unix/bsd/netbsdlike/openbsd/mod.rs

@@ -1660,6 +1660,12 @@ pub const MNT_WAIT: ::c_int = 1;
 pub const MNT_NOWAIT: ::c_int = 2;
 pub const MNT_LAZY: ::c_int = 3;
 
+// sys/_time.h
+pub const CLOCK_PROCESS_CPUTIME_ID: ::clockid_t = 2;
+pub const CLOCK_THREAD_CPUTIME_ID: ::clockid_t = 4;
+pub const CLOCK_UPTIME: ::clockid_t = 5;
+pub const CLOCK_BOOTTIME: ::clockid_t = 6;
+
 pub const LC_COLLATE_MASK: ::c_int = 1 << ::LC_COLLATE;
 pub const LC_CTYPE_MASK: ::c_int = 1 << ::LC_CTYPE;
 pub const LC_MONETARY_MASK: ::c_int = 1 << ::LC_MONETARY;