Display warning for every non-4:2:0 subsampling (previously was
displayed for 4:2:2 but also 4:4:4 is now normally supported).

This enables multithreaded swscale conversion newly added to FFmpeg 5.

According to the documentation, this may improve performance.

+ missing space before (R) mark
+ make NDI_PRINT_COPYRIGHT macro call look like function

audio_frame2 is defined actually as class, not struct - the incorrect
was the forward declaration, not the friend-clause.

NDI redist installer doesn't set NDILIB_REDIST_FOLDER environment
variable and installs to /usr/local/lib by default.

+ fixed too short allocated string - missed length of '/'

This reverts commit 880640a6.

Really remove headers from VideoMasterHD SDK when deploying.

needed for libjuice

- set generator to UNIX Makefiles
- set installation path explicitly to /usr/local, otherwise it installs
  to program files

By reducing bit-depth of audio, quantization noise is introduced. If the
bit depth is reduced by consistent rounding (either always down, always
up, or always to nearest) the quantization noise is correlated with the
input signal and percieved as distortion. Adding a small amount of noise
to the input signal before reducing the bit-depth causes random
rounding, which makes the noise uncorrelated and uniformly spread
through the whole spectrum.

NDI is already handled separately.

Do not group "free" SDKs - XIMEA was only one, anyway, NDI handled separately.

This allows having some formatting in FIXES.md, eg. for different minor
versions like that:

    #### 1.7.1
    - changes for 1.7.1
    - another fix in 1.7.1
    ### 1.7.2
    - fixes for 1.7.2

+ join the lines like beginning with spaces more inteligently

and build it unconditionaly.

Allows compile time -DUSE_NDI_VERSION override.

- added C guard to inclusion of stdbool.h in host.h
- misc.h - added MERGE macro - MERGE_ is already defined in host but
  this is for a general use, the MERGE_ is left in the host.h not to
  introduce additional dependency

+ warn if capturing 16-bit YCbCr

Removed separate NDI handling (branch ndi-build and build it as upstream (if SDK is found)
since NDI is now dynamically runtime loaded.

To avoid adding NDI library yet allowing user to install it separately and use it with UG.

Coverity doesn't provide ETag but a filename with content-disposition
header, eg.:

    content-disposition: attachment; filename="cov-analysis-linux64-2020.09.tar.gz"

- lavc in summary not yet in right row but better