find_type() does type comparisons based on tag name for struct/union/enum
but when it returns the previous tag (eg, from "struct foo;") the returned
type has a null symtab pointer, so setting the symtab pointer in the type
before calling find_type() only throws away the symtab. Thus, since
find_type() doesn't check the symtab pointer when comparing the types, set
the symtab pointer after calling find_type().
a19b7ec8f9