Bug#45288: pb2 returns a lot of compilation warnings on linux

Fix compiler warnings.

mysys/stacktrace.c:
  Tag unused parameters.
sql/sql_lex.cc:
  Variable becomes unused in non-debug builds. Also, no need to
  assert the obvious.

mysys/stacktrace.c

@@ -86,7 +86,9 @@ void my_print_stacktrace(uchar* stack_bottom __attribute__((unused)),
 
 #if BACKTRACE_DEMANGLE
 
-char __attribute__ ((weak)) *my_demangle(const char *mangled_name, int *status)
+char __attribute__ ((weak)) *
+my_demangle(const char *mangled_name __attribute__((unused)),
+            int *status __attribute__((unused)))
 {
   return NULL;
 }

sql/sql_lex.cc

@@ -1303,8 +1303,6 @@ int MYSQLlex(void *arg, void *yythd)
           }
           else
           {
-            const char* version_mark= lip->get_ptr() - 1;
-            DBUG_ASSERT(*version_mark == '!');
             /*
               Patch and skip the conditional comment to avoid it
               being propagated infinitely (eg. to a slave).
@@ -1313,7 +1311,6 @@ int MYSQLlex(void *arg, void *yythd)
             comment_closed= ! consume_comment(lip, 1);
             if (! comment_closed)
             {
-              DBUG_ASSERT(pcom == version_mark);
               *pcom= '!';
             }
             /* version allowed to have one level of comment inside. */