They are hacks added to reuse the same scaling function for
different formats and they may cause problems when SIMD
implementation of the same functions are used along with pure
C functions.

Make yuv2yuvX16_c a function pointer for yuv2yuvX(), so that the
function pointer becomes bitdepth-independent.

This duplicates the function fillPlane().

Remove duplicate "inC" and "_c" functions that do the same thing;
give each function that handles data and acts as a function pointer
a "_c" suffix; remove "_c" suffix from functions that are inherently
not optimizable. Remove inline keyword from functions that are only
used through function pointers.

Altivec sws code intentionally overreads buffers for better performance,
so we need to allocate larger buffers to handle that.

Signed-off-by: Ronald S. Bultje <rsbultje@gmail.com>

libswscale/x86/swscale_template.c:2072: warning: unused variable ‘canMMX2BeUsed’
libswscale/x86/swscale_template.c:2145: warning: unused variable ‘canMMX2BeUsed’
libswscale/x86/swscale_template.c:2209: warning: unused variable ‘chrVPixBuf’
libswscale/x86/swscale_template.c:2237: warning: unused variable ‘chrVSrcPtr’

That means it won't be allocated when not needed. Alongside
this, it fixes valgrind/fate-detected memory leaks.

Preparatory step to implement support for sizes > VOFW.

This allows to convert between formats of arbitrary width,
regardless of the value of VOF/VOFW.

Many functions have such a prefix, but do not actually use any
instructions or features from that set, thus giving the false
impression that swscale is highly optimized for a particular
system, whereas in reality it is not.

Interleave macros and code so that it's easier to find the
actual code that belongs to a function. Also reindent where
appropriate and remove dead code.

This allows cutting up the function in much smaller and easier-
to-maintain chunks.

If that flag is set, swScale() already proxies the call to
yuv2rgbXinC_full(). Therefore, this flag is never set when
yuv2packed1() is called.