For strrchr().  Fixes build failure.

Convert to 31 bit first, then right-shift with rounding to 16 bit.

Provide the full API.

This corrects a major mistake from commit 724a59aa - there was one
small thing that commit was supposed to do, and it failed.
AV_TIME_BASE is not a seek flag.

The class does not have any virtual methods, and thus the (debug-only)
destructor does not need to be virtual.

These are the default values already.

Avoid multiplication.  This is a speedup of 20%.

Replaces its own weird buffering code.

Code simplification.

Not necessary anymore, because we enable this flag unconditionally
now.

Make sure glibc gives us all features.

This is nearly 4 times faster than the "portable" algorithm.

Use some odd number that will expose problems with remaining samples
after optimized vector operations.

Run each unit test only once.  Using CPPUNIT_TEST_SUITE_REGISTRATION
from within the header meant that each unit class was registered again
for each source file that includes the header.