remove prototype extern int is_ptr_type()

because the function was already defined as an inline function
in the same header file.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>

Author: lucvoo

symbol.h

@@ -438,7 +438,6 @@ static inline struct symbol *lookup_keyword(struct ident *ident, enum namespace
 #define is_restricted_type(type) (get_sym_type(type) == SYM_RESTRICT)
 #define is_fouled_type(type) (get_sym_type(type) == SYM_FOULED)
 #define is_bitfield_type(type)   (get_sym_type(type) == SYM_BITFIELD)
-extern int is_ptr_type(struct symbol *);
 
 void create_fouled(struct symbol *type);
 struct symbol *befoul(struct symbol *type);