libsframe: add the SFrame library

libsframe is a library that allows you to:
- decode a .sframe section
- probe and inspect a .sframe section
- encode (and eventually write) a .sframe section.

This library is currently being used by the linker, readelf, objdump.
This library will also be used by the SFrame unwinder which is still
to be upstream'd.

The file include/sframe-api.h defines the user-facing APIs for decoding,
encoding and probing .sframe sections. A set of error codes together
with their error message strings are also defined.

Endian flipping is performed automatically at read and write time, if
cross-endianness is detected.

ChangeLog:

	* Makefile.def: Add libsframe as new module with its
	dependencies.
	* Makefile.in: Regenerated.
	* binutils/Makefile.am: Add libsframe.
	* binutils/Makefile.in: Regenerated.
	* configure: Regenerated
	* configure.ac: Add libsframe to host_libs.
	* libsframe/Makefile.am: New file.
	* libsframe/Makefile.in: New file.
	* libsframe/aclocal.m4: New file.
	* libsframe/config.h.in: New file.
	* libsframe/configure: New file.
	* libsframe/configure.ac: New file.
	* libsframe/sframe-error.c: New file.
	* libsframe/sframe-impl.h: New file.
	* libsframe/sframe.c: New file.

include/ChangeLog:

	* sframe-api.h: New file.

testsuite/ChangeLog:

	* libsframe/testsuite/Makefile.am: New file.
	* libsframe/testsuite/Makefile.in: Regenerated.
	* libsframe/testsuite/libsframe.decode/Makefile.am: New
	  file.
	* libsframe/testsuite/libsframe.decode/Makefile.in:
	  Regenerated.
	* libsframe/testsuite/libsframe.decode/decode.exp: New file.
	* libsframe/testsuite/libsframe.encode/Makefile.am:
	  Likewise.
	* libsframe/testsuite/libsframe.encode/Makefile.in:
	  Regenerated.
	* libsframe/testsuite/libsframe.encode/encode.exp: New file.
	* libsframe/testsuite/libsframe.encode/encode-1.c: Likewise.
	* libsframe/testsuite/libsframe.decode/be-flipping.c: Likewise.
	* libsframe/testsuite/libsframe.decode/frecnt-1.c: Likewise.
	* libsframe/testsuite/libsframe.decode/frecnt-2.c: Likewise.
	* libsframe/testsuite/libsframe.decode/DATA-BE: New file.
	* libsframe/testsuite/libsframe.decode/DATA1: Likewise.
	* libsframe/testsuite/libsframe.decode/DATA2: Likewise.