make myisam usable without threads (and even w/o pthread_t)

include/myisam.h

@@ -366,14 +366,18 @@ typedef struct st_sort_info
   SORT_KEY_BLOCKS *key_block,*key_block_end;
   /* sync things*/
   uint got_error, threads_running;
+#ifdef THREAD
   pthread_mutex_t mutex;
   pthread_cond_t  cond;
+#endif
 } SORT_INFO;
 
 
 typedef struct st_mi_sort_param
 {
+#ifdef THREAD
   pthread_t  thr;
+#endif
   IO_CACHE read_cache, tempfile, tempfile_for_exceptions;
   DYNAMIC_ARRAY buffpek;
   ulonglong unique[MI_MAX_KEY_SEG+1];

myisam/mi_check.c

@@ -2109,7 +2109,7 @@ err:
   Threaded repair of table using sorting
 
   SYNOPSIS
-    mi_repair_by_sort_r()
+    mi_repair_parallel()
     param		Repair parameters
     info		MyISAM handler to repair
     name		Name of table (for warnings)
@@ -2128,6 +2128,9 @@ err:
 int mi_repair_parallel(MI_CHECK *param, register MI_INFO *info,
 			const char * name, int rep_quick)
 {
+#ifndef THREAD
+  return mi_repair_by_sort(param, info, name, rep_quick);
+#else
   int got_error;
   uint i,key, total_key_length, istep;
   ulong rec_length;
@@ -2489,6 +2492,7 @@ err:
     share->pack.header_length=0;
   }
   DBUG_RETURN(got_error);
+#endif /* THREAD */
 }
 
 	/* Read next record and return next key */

myisam/sort.c

@@ -275,6 +275,7 @@ static ha_rows NEAR_F find_all_keys(MI_SORT_PARAM *info, uint keys,
 } /* find_all_keys */
 
 
+#ifdef THREAD
 /* Search after all keys and place them in a temp. file */
 
 pthread_handler_decl(thr_find_all_keys,arg)
@@ -542,6 +543,7 @@ int thr_write_keys(MI_SORT_PARAM *sort_param)
   my_free((gptr) mergebuf,MYF(MY_ALLOW_ZERO_PTR));
   return got_error;
 }
+#endif /* THREAD */
 
         /* Write all keys in memory to file for later merge */