In particular, in standard C, a struct or union must have at
least one member declared (ie. structs and unions cannot be
empty). Some compilers allow empty structs as an extension
and won't even issue a warning unless asked for it (eg, gcc
requires -pedantic). Some compilers allow empty structs as
an extension and will only treat it as an error if asked for
strict checking (eg Digital-Mars with -A). Some compilers
simply treat it as an error (eg MS Visual C/C++).

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Andreas Ericsson <ae@op5.se>