SSL: added version checks for ssl compression workaround.

The SSL_COMP_get_compression_methods() is only available as an API
function in OpenSSL 0.9.8+, require it explicitly to unbreak build
with OpenSSL 0.9.7.

src/event/ngx_event_openssl.c

diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
index 93d3f65..5e25b01 100644
--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -94,6 +94,7 @@
 
     OpenSSL_add_all_algorithms();
 
+#if OPENSSL_VERSION_NUMBER >= 0x0090800fL
 #ifndef SSL_OP_NO_COMPRESSION
     {
     /*
@@ -111,6 +112,7 @@
     }
     }
 #endif
+#endif
 
     ngx_ssl_connection_index = SSL_get_ex_new_index(0, NULL, NULL, NULL, NULL);