The 7zip, scrypt and stdout kernels differ from the others in their
function declarations somewhat. Unify them and substitute with macros.
Also remove a few superfluous (bogus) consts which were introduced in
the previous PR.
Substitute long parameter lists in ~2900 kernel function declarations
with macros. This cleans up the code, reduces probability of copy-paste
errors and highlights the differences between kernel functions. Also
reduces the size of the OpenCL folder by ~3 MB.
In preparation for the abstraction of long repetitive kernel function
declarations, rename the salt buffer pointers to *esalt_bufs. Also
declare them const where they are not.
