tests if an object has a specific tag
BOOL = hastag(OBJ_HANDLE,STR)
Tests if the object corresponding to OBJ_HANDLE has the tag STR. When OBJ_HANDLE is an array of handles HASTAG returns a logical array of the same size.
Rem: In order for this to work properly, the object's tag field must be a string containing keywords (or tags) separated by commas.