The entries in the current Versions file don't work as expected.
Since the first ALSA_0.9 has already snd_* global definitions, all
the rest are simply ignored. Some symbols (e.g. snd_hw_params_*)
indeed work because they have explicit symver definitions, but
ALSA_0.9.6 and later are all superfluous.
This patch clean up these useless entries. Also, the patch restricts
the matching patterns for _snd_* and __snd_* entries to reduce the
unneeded export symbols.
Export helper functions to convert dB level and range.
snd_tlv_*dB*() are to convert dB level or range directly from TLV data.
snd_ctl_*dB*() are to get dB level or range from a control element.