lavc: eliminate tb_unreliable()

If framerate estimation is enabled, it makes sense to always apply it,
instead of limiting it to a few specific cases.
disable -rpath-link on Solaris

The Solaris -rpath linker option parser is greedy.
build: add Solaris symbol versioning

The Solaris linker does not support globs in linker scripts for
symbol versioning (this is a GNU extension). Let's instead borrow
make_sunver.pl from GCC to make a description file that works
with the Solaris linker.