Fix various spelling errors

e.g.
- dont -> don't
- occurence -> occurrence
- succesfully -> successfully
- easyly -> easily

Also remove trailing space in selected files.

These changes span:
- server core
- Connect and Innobase storage engine code
- OQgraph, Sphinx and TokuDB storage engines

Related to MDEV-21769.

sql/sql_class.cc

@@ -6808,7 +6808,7 @@ void THD::binlog_prepare_row_images(TABLE *table)
 
   /**
     if there is a primary key in the table (ie, user declared PK or a
-    non-null unique index) and we dont want to ship the entire image,
+    non-null unique index) and we don't want to ship the entire image,
     and the handler involved supports this.
    */
   if (table->s->primary_key < MAX_KEY &&