Log message:
Remove libffi, pkgsrc version is the same.

Log message:
>From joerg in devel/libffi:
GAS doesn't like unified ARM syntax without explicitly told so.

Log message:
Import libffi-3.1 as wip/libffi.

The libffi library provides a portable, high level programming
interface to various calling conventions.  This allows a programmer to
call any function specified by a call interface description at
run-time.

Some programs may not know at the time of compilation what arguments
are to be passed to a function.  For instance, an interpreter may be
told at run-time about the number and types of arguments used to call
a given function.  Libffi can be used in such programs to provide a
bridge from the interpreter program to compiled code.

Ffi stands for Foreign Function Interface.  A foreign function
interface is the popular name for the interface that allows code
written in one language to call code written in another language.  The
libffi library really only provides the lowest, machine dependent
layer of a fully featured foreign function interface.  A layer must
exist above libffi that handles type conversions for values passed
between the two languages.