patch 8.2.3985: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more error messages to errors.h.
diff --git a/src/os_unix.c b/src/os_unix.c
index e22f146..9930680 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -7575,7 +7575,7 @@
 	    for (i = 0; signal_info[i].sig != -1; i++)
 		if (lc_signal == signal_info[i].sig)
 		    break;
-	    semsg("E368: got SIG%s in libcall()", signal_info[i].name);
+	    semsg(e_got_sig_str_in_libcall, signal_info[i].name);
 	}
 #  endif
 # endif