getdns: fix compilation without deprecated OpenSSL APIs

Since DSA is enabled, dsa.h is needed. Normally this header is included
implicitly with engine.h but with OPENSSL_API_COMPAT >= 0x10100000L ,
this is not so.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

libs/getdns/patches/010-openssl-deprecated.patch

@@ -0,0 +1,13 @@
+--- a/src/tls/val_secalgo.c
++++ b/src/tls/val_secalgo.c
+@@ -72,6 +72,10 @@
+ #include <openssl/engine.h>
+ #endif
+ 
++#ifdef USE_DSA
++#include <openssl/dsa.h>
++#endif
++
+ /** fake DSA support for unit tests */
+ int fake_dsa = 0;
+ /** fake SHA1 support for unit tests */