"CRF-max" support with VBV
This is a rather curious feature that may have more use than is initially obvious.
In CRF mode with VBV enabled, CRF-max allows the user to specify a quality level which the encoder will never go below, even due to the effects of VBV.
This is not the same as qpmax, which is not aware of issues like scene complexity.
Setting this WILL cause VBV underflows in any situation where the encoder would have needed to exceed the relevant CRF to avoid underflow.

Why might one want to do this even if it would cause VBV underflows?
In the case of streaming, particularly ultra-low-latency streaming, it may be preferable to drop frames than to display frames that are of too low a quality.
Thus, in extremely complex scenes, rather than display completely awful video, the streaming server could simply drop to a lower framerate.
Scenecuts, which normally look terrible under situations like single-frame VBV, could be handled by just displaying them a bit later and dropping frames to compensate.
In other words, it's better to see the scenecut 150ms delayed than for it to look like a blocky mess for 150ms.

On the caller-side, this would be handled by detecting the output size of x264's frames and dropping future frames to compensate if necessary.

This can also be used in normal encoding simply to ensure that VBV does not hurt quality too much (at the cost of potentially causing underflows).
This can help quite a lot when using single-frame VBV and sliced threads, where VBV can often be somewhat unstable.
Fix two nondeterminisms
Move noise reduction data into thread-specific data.
Use correct reference list for L1 temporal predictors.
Use x264_log in more places instead of fprintf
Shrink some arrays in x264_t
Also remove an unnecessary assignment from cache_load.
Save a few bits in slice headers
Don't override the maximum ref index in the slice header if it's the same as the default.
Also update the naming of the relevant variables in the PPS.
Fix link errors with newest gpac cvs
gpac decided to randomly break API and require us to use their own custom malloc and free.
Fix slightly wrong mp4 duration.
Add support for spaces to iPhone GAS preprocessor script
Fix typo in configure
Reformat profile restrictions in --fullhelp.

Put "no interlaced", "no lossless" on their own line to avoid them
running into the default options list.
Much more accurate B-skip detection at 2 < subme < 7
Use the same method that x264 uses for P-skip detection.
This significantly improves quality (1-6%), but at a significant speed cost as well (5-20%).
It also may have a very positive visual effect in cases where the inaccurate skip detection resulted in slightly-off vectors in B-frames.
This could cause slight blurring or non-smooth motion in low-complexity frames at high quantizers.
Not all instances of this problem are solved: the only universal solution is non-locally-optimal mode decision, which x264 does not currently have.

subme >= 7 or <= 2 are unaffected.
Faster x264_macroblock_encode_pskip
GCC is apparently unable to optimize out the calculation of a variable when it isn't used.
Two compatibility fixes
Add IA64 support in configure.
Make a bunch of small functions ALWAYS_INLINE
Probably no real effect for now, but needed for the next patch.
Overhaul macroblock_cache_rect
Unify the rectangle functions into a single one similar to ffmpeg's fill_rectangle.
Remove all cases of variable-size cache_rect calls; create a function-pointer-based system for handling such cases.
Should greatly decrease code size required for such calls.
Various motion estimation optimizations
Faster method of checking MV range.
Predict MVs and cache MVs/MVDs for bidir qpel-RD.
A whole bunch of other minor optimizations.
Slightly better performance and compression.
Reduce stack usage of b-adapt 2's trellis
Also remove some redundant code.
Split up analyse_init
Save some time by avoiding some unnecessary inits and moving other parts to per-thread init.
Cosmetics: use sizeof() where appropriate
Fix stack alignment in sliced threads
Could cause crashes when called from non-GCC-compiled applications.