bug #10166 (Signed byte values cause data to be padded)

The AsBinary function returns VARCHAR data type with binary collation.
It can cause problem for clients that treat that kind of data as
different from BLOB type.
So now AsBinary returns BLOB.

mysql-test/r/gis.result

@@ -661,3 +661,13 @@ POINT(10 10)
 select (asWKT(geomfromwkb((0x010100000000000000000024400000000000002440))));
 (asWKT(geomfromwkb((0x010100000000000000000024400000000000002440))))
 POINT(10 10)
+create table t1 (g GEOMETRY);
+select * from t1;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def	test	t1	t1	g	g	255	4294967295	0	Y	144	0	63
+g
+select asbinary(g) from t1;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def					asbinary(g)	252	8192	0	Y	128	0	63
+asbinary(g)
+drop table t1;

mysql-test/t/gis.test

@@ -364,3 +364,10 @@ select (asWKT(geomfromwkb((0x000000000140240000000000004024000000000000))));
 select (asWKT(geomfromwkb((0x010100000000000000000024400000000000002440))));
 
 # End of 4.1 tests
+
+--enable_metadata
+create table t1 (g GEOMETRY);
+select * from t1;
+select asbinary(g) from t1;
+--disable_metadata
+drop table t1;

sql/item_geofunc.h

@@ -32,6 +32,7 @@ class Item_geometry_func: public Item_str_func
   Item_geometry_func(Item *a,Item *b,Item *c) :Item_str_func(a,b,c) {}
   Item_geometry_func(List<Item> &list) :Item_str_func(list) {}
   void fix_length_and_dec();
+  enum_field_types field_type() const  { return MYSQL_TYPE_GEOMETRY; }
 };
 
 class Item_func_geometry_from_text: public Item_geometry_func
@@ -67,6 +68,7 @@ class Item_func_as_wkb: public Item_geometry_func
   Item_func_as_wkb(Item *a): Item_geometry_func(a) {}
   const char *func_name() const { return "aswkb"; }
   String *val_str(String *);
+  enum_field_types field_type() const  { return MYSQL_TYPE_BLOB; }
 };
 
 class Item_func_geometry_type: public Item_str_func