Static loop unrolling fails if loop body contains a struct

[msprotz]

See commit fcc0213 which works around the issue.

Basically, if a struct is used in the loop body, then it generates a compound literal that contains a comma, and then the preprocessor thinks that the macro KRML_MAYBE_UNROLL(..., <>) receives too many arguments.

From https://stackoverflow.com/questions/13842468/comma-in-c-c-macro#19841470, which is moderately useful, two solutions are:

• #define LOOP_BODY(...) __VA_ARGS__ and then have krml emit KRML_MAYBE_UNROLL(..., LOOP_BODY(...))
• #define COMMA , and then have krml print at the last minute using COMMA instead of ,

The former seems easier to implement