Removed all structure packing directives. Protocol header fields are naturally aligne...

Removed all structure packing directives. Protocol header fields are naturally aligned by design.
(Earlier, the 14-byte ethernet header screwed this up, this had already been fixed by adding two pad bytes.)
Assumption is that compilers do not align with larger-than-sizeof(type) boundaries.
Pre-tag PRE_PACK_REMOVE. Post-tag POST_TAG_REMOVE.