BUILD: fix ssl_sample.c when building against BoringSSL

BoringSSL does not have X509_get_X509_PUBKEY
let our emulation level define that for BoringSSL as well

Build log:

src/ssl_sample.o: In function `smp_fetch_ssl_x_key_alg':
/home/travis/build/haproxy/haproxy/src/ssl_sample.c:592: undefined reference to `X509_get_X509_PUBKEY'
clang-7: error: linker command failed with exit code 1 (use -v to see invocation)
Makefile:860: recipe for target 'haproxy' failed
make: *** [haproxy] Error 1

travis-ci: https://travis-ci.com/github/haproxy/haproxy/jobs/351670996
diff --git a/include/haproxy/openssl-compat.h b/include/haproxy/openssl-compat.h
index 34fe6cb..acdc9c5 100644
--- a/include/haproxy/openssl-compat.h
+++ b/include/haproxy/openssl-compat.h
@@ -81,6 +81,9 @@
 
 #endif // OpenSSL < 0.9.8
 
+#if (((HA_OPENSSL_VERSION_NUMBER < 0x1000000fL) || defined(OPENSSL_IS_BORINGSSL)) && !defined(X509_get_X509_PUBKEY))
+#define X509_get_X509_PUBKEY(x) ((x)->cert_info->key)
+#endif
 
 #if (HA_OPENSSL_VERSION_NUMBER < 0x1000000fL)
 /* Functions introduced in OpenSSL 1.0.0 */
@@ -98,10 +101,6 @@
 	return 1;
 }
 
-#ifndef X509_get_X509_PUBKEY
-#define X509_get_X509_PUBKEY(x) ((x)->cert_info->key
-#endif
-
 #endif
 
 #if (HA_OPENSSL_VERSION_NUMBER < 0x1000100fL)