* flags.h (warn_padded, warn_packed): Add global var decls.
* toplev.c (warn_padded, warn_packed): Add global var defns.
(W_options): Add warnings `-Wpacked' and `-Wpadded'.
* stor-layout.c (layout_record): Add local variable `type'
to hold often-used TREE_TYPE (field).  Add local variable
`unpacked_align' to hold alignment that would be in force
if no `packed' attribute were present.  Warn if `packed' attribute
is unnecessary, or even harmful.  Warn when gcc inserts padding
to satisfy alignment requirements of members.  Use NULL_TREE
when checking whether var_size is set.
* invoke.texi: Document new flags.

Co-Authored-By: Geoff Keating <geoffk@cygnus.com>

From-SVN: r30770