Eliminate warnings noticed by VC7. This includes fixing my_mmap() on

Windows to call CreateFileMapping() with correct arguments, and
propogating the introduction of query_id_t to everywhere query ids are
passed around. (Bug #8826)


libmysql/libmysql.c:
  Make implicit cast explicit
myisam/mi_open.c:
  Make cast of value to smaller data size explicit
myisam/mi_packrec.c:
  Cast file size (my_off_t) to size_t for mmap
mysys/my_mmap.c:
  Fix Windows version of my_mmap() to use the right parameters
  for call to CreateFileMapping()
sql/field.cc:
  Use temporary value of correct type
sql/field.h:
  Use query_id_t for query_id value
sql/ha_berkeley.cc:
  Fix flag check
sql/ha_innodb.h:
  Use query_id_t for query_id value
sql/handler.cc:
  Explain opt_using_transactions calculation, and add cast
sql/handler.h:
  Fix forward declaration of COND
sql/item.cc:
  Fix val_bool() tests of val_int() to avoid implicit cast
sql/item_cmpfunc.cc:
  Fix typo in switch label
sql/item_func.cc:
  Make implicit cast explicit
sql/item_strfunc.cc:
  Now that query_id is a query_id_t, need to cast it to a ulong here
sql/item_subselect.cc:
  Fix test of value
sql/log.cc:
  Cast my_off_t used for file size to size_t for memory allocation
  Also cast my_off_t when using it to calculate the number of pages for TC log
  Cast total_ha_2pc to uchar when saving it
sql/mysql_priv.h:
  Move up query_id definition so it can be used more widely
sql/opt_range.cc:
  Add unused delete operator to prevent compiler warning
sql/set_var.cc:
  Cast value for max_user_connections
sql/sql_cache.cc:
  Remove unused label
sql/sql_class.h:
  Fix query id values to be of type query_id_t
sql/sql_db.cc:
  Move variable only used inside #ifdef within the #ifdef
sql/sql_help.cc:
  Remove unused label
sql/sql_insert.cc:
  Use query_id_t for query id values
sql/sql_lex.h:
  Add unused delete operator to prevent compiler warning
sql/sql_select.cc:
  Remove unused variable
  Make cast of value explicit
sql/sql_select.h:
  Use query_id_t for query id values
sql/sql_table.cc:
  Make comparison to function pointer explicit
sql/sql_update.cc:
  Use query_id_t for query id values
sql/table.h:
  Use query_id_t for query id values
strings/ctype-simple.c:
  Add cast of long value to (char) in expression
strings/ctype-ucs2.c:
  Add cast of long value to (char) in expression
strings/ctype-utf8.c:
  Make cast to smaller size explicit

libmysql/libmysql.c

@@ -3608,7 +3608,7 @@ static void fetch_long_with_conversion(MYSQL_BIND *param, MYSQL_FIELD *field,
     if (is_unsigned)
       data= ulonglong2double(value);
     else
-      data= value;
+      data= (double)value;
     doublestore(buffer, data);
     *param->error= is_unsigned ?
                    ((ulonglong) value) != ((ulonglong) (*(double*) buffer)) :