We access some variable values using casts like *(long *) buff
that may cause crashes on some platforms (e.g. solaris 64) if buff is
not properly aligned.
Fix: align the buffer used.


include/my_global.h:
  Fix for bug #23810: Server crashes on various "show status ..." commands
    - MY_DIV_UP(A, B) macro introduced, which devides A then rounds up by B.
    - MY_ALIGNED_BYTE_ARRAY(N, S, T) macro introduced, which declares an S-byte long
      (aligned) N array of type T.
sql/sql_show.cc:
  Fix for bug #23810: Server crashes on various "show status ..." commands
    - align the buffer used.