i'm confused as to why these fields exist, since the typical
implementation of a "temporary alloc" would be something like alloca(),
and alloca() is usually just inlined code that adjusts the stack
pointer, which is not a function whose address could be taken.
this breaks the API/ABI and will require a note in the ChangeLog.
possibly we could revisit the idea of "temporary allocations" by using
C99 variable length arrays. this would have the advantage of being
standardized, unlike alloca().
of the same field on the wire (Fixes#91)
t/generated-code2/test-generated-code2.c: add a test case for merging
messages
t/test-full.proto: expand message definitions to test for merging nested
messages
