8-bit build for x265 encoding

The standard versions of AppImage, the pre-compiled binary and any build you do yourself, is the multibit version by default, which allows rendering of the x265 codec at all supported bit-depths. If instead you prefer to compile the 8-bit only version, there is the option to do so. The 8-bit version does not have 10/12-bit encoding of x265; the 8-bit version works on 8-bit bytes which is the standard word size for computers, while the multibit version has to use 2 words to contain all 10/12 bits so you might expect rendering to be slower. Various tests show that there is little or no difference in performance between the two versions, especially on modern systems, so the standard multibit version is the recommended one. If you have a need to compile the 8-bit version first perform the following steps:

1. Move to the thirdparty directory: cd /path_to/cinelerra-5.1/thirdparty
2. Edit the file "Makefile" by changing these 3 lines to switch the # comment character like this:
   

   #x265.cfg_vars?=chmod +x ./configure; chmod +x ./multilib.sh;
   x265.cfg_vars?=$(call cmake_config,source)
   x265.cfg_params?= -DENABLE_SHARED=no -DENABLE_CLI=no

3. Then delete or rename the 3 patch files in thirdparty/src with names of x265-xxxxx.patchx.

Using the 8-bit version will result in an error if you use the Render formats h265-10bit and h265-12bit. Error message on the startup window is something like this:

[libx265 @ 0x7fa00e643880] Specified pixel format yuv422p1xle is not supported by the libx265 encoder.