Change license to 3-clause BSD.

Add man pages.
Replace typedef unsigned char u_int8 etc with stdint.h types.
Update to new autotools.
Generate html versions from man pages.
Reflect the manpages in the homepage.
Fix recvmsg() on Solaris.
Detect clang for compiling.
Fix generating a rpm package.
Fix building on Windows.

If building from the file downloaded from github,
run the following first to regenerate the build tools:
$ aclocal
$ automake --add-missing --force-missing
$ autoconf

Release 1.21

rtptools