no EXPORT or GLOBAL section - unitialized variable being used!

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