Fix for Bug#4030 "Client side conversion string -> date type doesn't

work (prepared statements)" and after-review fixes:
- str_to_TIME renamed to str_to_datetime to pair with str_to_time
- functions str_to_time and str_to_TIME moved to sql-common
- send_data_str now supports MYSQL_TYPE_TIME, MYSQL_TIME_DATE,
  MYSQL_TIME_DATETIME types of user input buffers.
- few more comments in the client library
- a test case added.

include/mysql.h

@@ -55,6 +55,7 @@ typedef int my_socket;
 #endif /* _global_h */
 
 #include "mysql_com.h"
+#include "mysql_time.h"
 #include "mysql_version.h"
 #include "typelib.h"
 
@@ -533,23 +534,6 @@ enum enum_mysql_stmt_state
   MYSQL_STMT_FETCH_DONE
 };
 
-/* 
-  client TIME structure to handle TIME, DATE and TIMESTAMP directly in 
-  binary protocol 
-*/
-enum mysql_st_timestamp_type { MYSQL_TIMESTAMP_NONE, MYSQL_TIMESTAMP_DATE, 
-                               MYSQL_TIMESTAMP_FULL, MYSQL_TIMESTAMP_TIME };
-
-typedef struct mysql_st_time 
-{
-  unsigned int  year,month,day,hour,minute,second;
-  unsigned long second_part;  
-  my_bool       neg;
-
-  enum mysql_st_timestamp_type time_type;
-  
-} MYSQL_TIME;
-
 
 /* bind structure */
 typedef struct st_mysql_bind