Empty Macros

[nosracd]

The *_decode_array_cleanup macros defined in lcm/lcm_coretypes.h have an empty definition. For example:

#define __double_decode_array_cleanup(p, sz) \
    {                                        \
    }

This produces unused parameter warnings when compiling C code outputted from lcm-gen.

It looks like these macros should just be removed, but doing so would be a breaking change and not possible without incrementing the major release version.