Change suggested by Kaarthik Sivakumar <[email protected]> -

Change suggested by Kaarthik Sivakumar <[email protected]> -
various BGP structures have sizes that aren't multiples of the size of
the most strictly aligned type in the structure, so the compiler will
pad them out to that size; we should add #defines for the real size, if
we don't already have them, and use them rather than the result of
"sizeof".

Do that even for structures that have sizes that are multiples of the
size of the most strictly aligned type in the structure, as some
compilers (e.g., at least some versions of GCC for ARM) apparently pad
structures to multiples of 4 bytes.

Add a missing TCHECK2 call.