also reformatted types

also rearranged comment descriptions of meaning of optimizations
(now tagfield clearly implies manyshapes)

eg. malloc(sizeof(t)) should be malloc(sizeof(struct t)) !!

single char ids like f, p should be avoided;
renamed types as first, second, third etc

in a nice state now..
-- output file is selected and stored globally rather than being
   passed around all the time;
-- implicit NULL tests are now explicit;
-- some details of the generated code are different now.

added prototype rebuild stuff in a comment (for cutting and pasting);
added decln, param and shape.

TRUE if we're optimizing (temporary code) or FALSE otherwise

in generated code

required a few changes to impln_declns

removed print/write option - always written;
opt = TRUE by default; added -n "no optimize" option..