[Serusers] Some patches for integration

[Maxim Sobolev]

Folks,

Attached please find several patches for ser 0.8.10. They do the following:

1. Removes hardcoded `/usr/local' from Makefiles and replaces it with
LOCALBASE variable setable in the top Makefile.defs. This should make
life of packagers easier.

2. Allows to override PREFIX variable with something else from environment.

3. Adds support for FreeBSD doc/man directories layout.

4. Adds some missed -I's into radius modules.

5. Fixes radius modules to use the same symbolic avp names as in dictionary.

6. Adds support for recording source port in msg structure and adds it
in "Noisy feedback". This should be extremely useful for debugging various
SIP&NAT scenarios and later could be re-used to implement `rport' support
described in my previous message.

It would be nice to have those patches integrated into the next release.

Thanks!

-Maxim