libscrypt: New package

libscrypt: New package

Signed-off-by: Stefan Sørensen <stefan.sorensen@spectralink.com>
[Thomas:
 - Add entry to DEVELOPERS file for the new package
 - Add dependency on !BR2_STATIC_LIBS, because the Makefile
   unconditionally builds a shared library
 - Use the "github" helper function to define <pkg>_SITE, get rid of
   <pkg>_SOURCE.
 - License is BSD-2c, not just BSD.
 - Add <pkg>_LICENSE_FILES variable.
 - Define LIBSCRYPT_DISABLE_STACK_PROTECTOR inside the
   BR2_TOOLCHAIN_HAS_SSP condition, and move from a
   LIBSCRYPT_POST_EXTRACT_HOOKS to a LIBSCRYPT_POST_PATCH_HOOKS.
 - Pass $(TARGET_CONFIGURE_OPTS) instead of just passing CC.
 - Pass $(TARGET_MAKE_ENV) when calling $(MAKE).]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>