The old version of `FLAC__bitwriter_write_raw_uint32()` assumes that the
unused bits of the `val` argument are equal to zero, but don't check it.

This patch adds a new version of that function which does have the check
and then calls a new function `FLAC__bitwriter_write_raw_uint32_nocheck()`
which behaves like the old one.

Code updated to use these two functions as needed.

Patch-from: lvqcl <lvqcl.mail@gmail.com>