Fixes #61 (and closes #62)
usrsctplib was built against commit sctplab/usrsctp@c53d43ee76673ee281806497eb43750c239c145f

Updates usrsctp to latest code c53d43ee76673ee281806497eb43750c239c145f. Updates build instructions with new repository and some notes.

Deletes the lib/native/freebsd* directories because we do not plan on maintaining FreeBSD support and nobody has stepped forward to support them for a long time now.

Deletes the files which implement Speex with pure Java because we are not using them anyway and we do not want the obsolete dependency on jspeex.

ice4j SVN revision 506: Fixes a stack overflow reported by James B. Byrne, investigated by Danny van Heumen.

Updates the JNA library to version 4.1.0 because it is dual-licensed under LGPL 2.1 and Apache License 2.0.

Moves the FFmpeg and G722 JNI libraries from libjitsi to jitsi-lgpl-dependencies because they statically link to LGPL objects.

Fixes invocations of JNI functions with incorrect arguments, modifications of JNI values which are to be treated as const, dangerous discards of return values of JNI functions.

ICE4J revision 471: Fixes technical errors in method invocations. Optimizes type checks on packet send and receive.

Implements AES and HMAC-SHA1 using OpenSSL. Automatically selects the fastest AES implementation at runtime among BouncyCastle, OpenSSL, Sun JCE and Sun PKCS#11.

FMJ revision 91: Fixes a thread leak (and related memory leaks) when an RTP receive stream is never played back.

FMJ revision 81: Mitigates deadlocks related to synchronization source identifier (SSRC)-related information lookup.