Makefile: Ensure that a change of common_opencl_pbkdf2.h will result in
re-compile of common_opencl_pbkdf2.o and opencl_mscash2_fmt.o.

Similar lines should be added for a bunch of formats that depend on header
files, especially where things like MAX_KEYS_PER_CRYPT or ITERATIONS are
present in the header file.
Merge branch 'unstable-jumbo' into bleeding-jumbo

* unstable-jumbo:
  Makefile: Ensure that a change of common_opencl_pbkdf2.h will result in re-compile of common_opencl_pbkdf2.o and opencl_mscash2_fmt.o.