Clean up error handling

core/os/os_openbsd.odin

@@ -419,7 +419,7 @@ close :: proc(fd: Handle) -> Errno {
 	if result == -1 {
 		return Errno(get_last_error())
 	}
-	return ERROR_NONE
+	return nil
 }
 
 // If you read or write more than `SSIZE_MAX` bytes, OpenBSD returns `EINVAL`.
@@ -476,7 +476,7 @@ rename :: proc(old_path, new_path: string) -> Errno {
 	if res == -1 {
 		return Errno(get_last_error())
 	}
-	return ERROR_NONE
+	return nil
 }
 
 remove :: proc(path: string) -> Errno {
@@ -486,7 +486,7 @@ remove :: proc(path: string) -> Errno {
 	if res == -1 {
 		return Errno(get_last_error())
 	}
-	return ERROR_NONE
+	return nil
 }
 
 make_directory :: proc(path: string, mode: mode_t = 0o775) -> Errno {
@@ -496,7 +496,7 @@ make_directory :: proc(path: string, mode: mode_t = 0o775) -> Errno {
 	if res == -1 {
 		return Errno(get_last_error())
 	}
-	return ERROR_NONE
+	return nil
 }
 
 remove_directory :: proc(path: string) -> Errno {
@@ -506,7 +506,7 @@ remove_directory :: proc(path: string) -> Errno {
 	if res == -1 {
 		return Errno(get_last_error())
 	}
-	return ERROR_NONE
+	return nil
 }
 
 is_file_handle :: proc(fd: Handle) -> bool {
@@ -638,7 +638,7 @@ _closedir :: proc(dirp: Dir) -> Errno {
 	if rc != 0 {
 		return Errno(get_last_error())
 	}
-	return ERROR_NONE
+	return nil
 }
 
 @private
@@ -760,7 +760,7 @@ set_current_directory :: proc(path: string) -> (err: Errno) {
 	if res == -1 {
 		return Errno(get_last_error())
 	}
-	return ERROR_NONE
+	return nil
 }
 
 exit :: proc "contextless" (code: int) -> ! {