yaws dependency on crypto:sha/1 deprecated

[rsharvey]

ERL: OTP 17.4
eoxdm: master

This is artifact of using 17.4, ignore if you want.

When compiling yaws, the dependency on crypto:sha/1 causes the build to fail. It is deprecated. Changed the rebar.config, removed "warnings_as_errors" and added "nowarn_deprecated_type".

{erl_opts, [%% OTP R11 - R15B -> yaws_sendfile_drv or compat_send
            {platform_define,
             "R1([1-4]|5[AB]-).*(linux|freebsd|darwin)", 'HAVE_YAWS_SENDFILE'},
            {platform_define, "R1([1-4]|5[AB]-)", 'NO_FILE_SENDFILE'},
            no_debug_info,
            {src_dirs, ["src", "examples/src"]},
           nowarn_deprecated_type]}.