alien-map: Check error from gegl_cl_set_kernel_args
noise-cell: remove static keywords

static keyword is not supported by OpenCL 1.1.
See Ch. 6.8 Restrictions, letter g)
noise-cell: Use f suffix for float constants.

Unsuffixed literal has type double (taken from c99 specs).
Fixes clang warnings:
warning: double precision constant requires cl_khr_fp64, casting to single precision
red-eye-removal: Use f suffix for float constants