refine librtmp, remove the ssl functoins, refine the type2string memory alloc to static

@@ -239,14 +239,19 @@ int srs_publish_stream(srs_rtmp_t rtmp)
 
 const char* srs_type2string(int type)
 {
+    static const char* audio = "Audio";
+    static const char* video = "Video";
+    static const char* data = "Data";
+    static const char* unknown = "Unknown";
+    
     switch (type) {
-        case SRS_RTMP_TYPE_AUDIO: return "Audio";
-        case SRS_RTMP_TYPE_VIDEO: return "Video";
-        case SRS_RTMP_TYPE_SCRIPT: return "Data";
-        default: return "Unknown";
+        case SRS_RTMP_TYPE_AUDIO: return audio;
+        case SRS_RTMP_TYPE_VIDEO: return video;
+        case SRS_RTMP_TYPE_SCRIPT: return data;
+        default: return unknown;
     }
     
-    return "Unknown";
+    return unknown;
 }
 
 int srs_read_packet(srs_rtmp_t rtmp, int* type, u_int32_t* timestamp, char** data, int* size)
@@ -355,14 +360,6 @@ int srs_write_packet(srs_rtmp_t rtmp, int type, u_int32_t timestamp, char* data,
     return ret;
 }
 
-int srs_ssl_enabled()
-{
-#ifndef SRS_AUTO_SSL
-    return false;
-#endif
-    return true;
-}
-
 int srs_version_major()
 {
     return ::atoi(VERSION_MAJOR);

@@ -109,6 +109,8 @@ int srs_publish_stream(srs_rtmp_t rtmp);
 *     SRS_RTMP_TYPE_VIDEO to "Video"
 *     SRS_RTMP_TYPE_SCRIPT to "Data"
 *     otherwise, "Unknown"
+* @remark user never free the return char*, 
+*   it's static shared const string.
 */
 const char* srs_type2string(int type);
 /**
@@ -132,14 +134,6 @@ int srs_read_packet(srs_rtmp_t rtmp, int* type, u_int32_t* timestamp, char** dat
 int srs_write_packet(srs_rtmp_t rtmp, int type, u_int32_t timestamp, char* data, int size);
 
 /**
-* whether srs is compiled with ssl,
-* that is, compile srs with ssl: ./configure --with-ssl,.
-* if no ssl, complex handshake always error.
-* @return 0 for false, otherwise, true.
-*/
-int srs_ssl_enabled();
-
-/**
 * get protocol stack version
 */
 int srs_version_major();