Add intrinsics.syscall_bsd

This is a BSD-style syscall that checks for a high Carry Flag as the
error state. If the CF is high, the boolean return value is false, and
if it is low (no errors) then the boolean return value is true.

core/sys/unix/sysctl_freebsd.odin

@@ -5,14 +5,15 @@ import "base:intrinsics"
 
 sysctl :: proc(mib: []i32, val: ^$T) -> (ok: bool) {
 	mib := mib
-	result_size := i64(size_of(T))
+	result_size := u64(size_of(T))
 
-	res := intrinsics.syscall(SYS_sysctl,
+	res: uintptr
+	res, ok = intrinsics.syscall_bsd(SYS_sysctl,
 		uintptr(raw_data(mib)), uintptr(len(mib)),
 		uintptr(val), uintptr(&result_size),
 		uintptr(0), uintptr(0),
 	)
-	return res == 0
+	return
 }
 
 // See /usr/include/sys/sysctl.h for details