BTREE-indexes in HEAP tables can now be used to optimize ORDER BY

Don't read character set files if we are using only the default charset. In most cases the user will not anymore get a warning about missing character set files
Compare strings with space extend instead of space strip. Now the following comparisons holds:  "a" == "a " and "a\t" < "a". (Bug #3152).
Note: Because of the above fix, one has to do a REPAIR on any table that has an ascii character < 32 last in a CHAR/VARCHAR/TEXT columns.


heap/hp_hash.c:
  Comments and DBUG information
include/my_handler.h:
  Updated prototype for mi_compare_text
myisam/ft_boolean_search.c:
  Updated calls to mi_compare_text
myisam/ft_nlq_search.c:
  Updated calls to mi_compare_text
myisam/ft_parser.c:
  Updated calls to mi_compare_text
myisam/ft_stopwords.c:
  Updated calls to mi_compare_text
myisam/ft_update.c:
  Updated calls to mi_compare_text
myisam/mi_check.c:
  Updated calls to mi_compare_text
myisam/mi_search.c:
  Changed all string comparisons that removed end space to instead extend the shorter string with space
myisam/mi_unique.c:
  Updated calls to mi_compare_text
myisam/mi_write.c:
  Updated calls to mi_compare_text
myisam/myisam_ftdump.c:
  Removed compiler warning
mysql-test/r/ctype_collate.result:
  Fixed wrong result
mysql-test/r/heap_btree.result:
  More tests
mysql-test/t/heap_btree.test:
  more tests
mysys/charset.c:
  Don't read charsets if we are only using default charset
  Don't require 'init_available_charsets' to succeed.
mysys/my_handler.c:
  Compare strings with space extend instead of space strip
mysys/tree.c:
  Fixed code to get better results for range optimzier
sql/field.cc:
  Compare strings with space extend instead of space strip
sql/filesort.cc:
  Compare strings with space extend instead of space strip
sql/ha_heap.cc:
  Created bit map for keys that are using BTREE. This allows the optimzer to use BTREE's for sorting
sql/ha_heap.h:
  Created bit map for keys that are using BTREE. This allows the optimzer to use BTREE's for sorting
strings/ctype-big5.c:
  Compare strings with space extend instead of space strip
strings/ctype-czech.c:
  Indentation cleanup. Should be fixed to use space extend
strings/ctype-gbk.c:
  Compare strings with space extend instead of space strip
strings/ctype-latin1.c:
  Compare strings with space extend instead of space strip
  Added missing my_hash_sort_latin1_de function
strings/ctype-mb.c:
  For binary strings, don't remove end space when comparing
strings/ctype-simple.c:
  Compare strings with space extend instead of space strip
strings/ctype-sjis.c:
  Compare strings with space extend instead of space strip
strings/ctype-tis620.c:
  Added comments that we should fix end space handling
strings/ctype-ucs2.c:
  indentation fixes
strings/ctype-utf8.c:
  Added comments that we should fix end space handling
strings/ctype-win1250ch.c:
  Added comments that we should fix end space handling

mysql-test/t/heap_btree.test

@@ -110,7 +110,13 @@ drop table t1;
 
 create table t1 (btn char(10) not null, key using BTREE (btn)) engine=heap;
 insert into t1 values ("hello"),("hello"),("hello"),("hello"),("hello"),("a"),("b"),("c"),("d"),("e"),("f"),("g"),("h"),("i");
-explain select * from t1 where btn like "q%";
+explain select * from t1 where btn like "i%";
+explain select * from t1 where btn like "h%";
+explain select * from t1 where btn like "a%";
+explain select * from t1 where btn like "b%";
+# For the following the BTREE MAY notice that there is no possible matches
+select * from t1 where btn like "ff%";
+select * from t1 where btn like " %";
 select * from t1 where btn like "q%";
 alter table t1 add column new_col char(1) not null, add key using BTREE (btn,new_col), drop key btn;
 update t1 set new_col=left(btn,1);