One more tweak to py-m2crypto (ideally also upstream)

[Viktor Dukhovni]

On my system OpenSSL 1.1.0 is configured with no RIPEMD160 support.

    $ egrep '^OPT' /var/db/ports/security_openssl-devel/options | sort
    OPTIONS_FILE_SET+=ASM
    OPTIONS_FILE_SET+=DH
    OPTIONS_FILE_SET+=EC
    OPTIONS_FILE_SET+=MAN3
    OPTIONS_FILE_SET+=SHARED
    OPTIONS_FILE_SET+=SSE2
    OPTIONS_FILE_SET+=THREADS
    OPTIONS_FILE_SET+=TLS1
    OPTIONS_FILE_SET+=TLS1_1
    OPTIONS_FILE_UNSET+=ASYNC
    OPTIONS_FILE_UNSET+=IDEA
    OPTIONS_FILE_UNSET+=JPAKE
    OPTIONS_FILE_UNSET+=MD2
    OPTIONS_FILE_UNSET+=MD4
    OPTIONS_FILE_UNSET+=MDC2
    OPTIONS_FILE_UNSET+=NEXTPROTONEG
    OPTIONS_FILE_UNSET+=RC2
    OPTIONS_FILE_UNSET+=RC4
    OPTIONS_FILE_UNSET+=RC5
    OPTIONS_FILE_UNSET+=RFC3779
    OPTIONS_FILE_UNSET+=RMD160
    OPTIONS_FILE_UNSET+=SCTP
    OPTIONS_FILE_UNSET+=SSL3
    OPTIONS_FILE_UNSET+=ZLIB

This results in a non-working M2Crypto build, which compiles and
with a warning about a missing prototype, installs, but fails to
load with an unresolved symbol.

The solution was to change SWIG/_evp.i, to take compile-time algorithm
disablement into account.  For me, just the below was sufficient:

    #ifndef OPENSSL_NO_RMD160
    %rename(ripemd160) EVP_ripemd160;
    extern const EVP_MD *EVP_ripemd160(void);
    #endif

M2Crypto really should not be using the direct EVP algorithm
accessors, rather it should be using EVP_get_digestbyname(3).

-- 
	Viktor.