add opaque configuration options in the generated TLB file
add opaque configuration options in the generated TLB file

This commit adds the 'alignment' and 'marshal_as' options
to the <opaque> elements of the generated TLB file. These
options will be silently ignored by Typelib, but can be
used by orogen to determine the opaque setup for types
imported from other toolkits.

doudou/modelkit-component,doudou/modelkit-component