conditionals. In particular the requirement in sad_00 that 'h' be 8 or 16 was
being violated by yuvdenoise and the program was mysteriously coredumping.
IF "user input" (in this case a parameter from a user program into a library)
can cause a program to segfault THEN that condition SHOULD BE CHECKED and
a meaninful error given.
After enabling the checks the cause of the problem was immediately known:
**ERROR: [yuvdenoise] sad_00: h != [8|16], (32)
