Infinite loop / memory leak

[auxym]

Repro:

1. Clone this repository: https://github.com/hathach/tinyusb
2. In the root, run c2nim --header --nep1 --skipinclude --skipcomments src/class/hid/hid.h

On my laptop, with c2nim v0.9.18, this never seems to stop running, and after a couple minutes, it's up to multiple GBs of memory use, the system is paging, and c2nim slows to a crawl (at which point I kill it).

Warning: the entire library is a huge soup of macros.