bufferp() - identifies whether a given variable is a buffer
int bufferp( mixed arg );
Return 1 if 'arg' is a buffer value and zero (0) otherwise.
int is_buffer = bufferp( allocate_buffer(10) ); // 1
int is_buffer = bufferp( "Foo" ); // 0
mapp(3), stringp(3), pointerp(3), objectp(3), intp(3), bufferp(3),
floatp(3), functionp(3), nullp(3), undefinedp(3), errorp(3)