Use {.reorder: on.} by default

[genotrance]

Setting this pragma by default will help all wrapper creators considering C/C++ is capable of forward references.

Need to table this for the near term since it is only working correctly in 0.19.0 devel and nimgen and wrappers need to continue to support older versions of Nim. Perhaps nimgen could do a Nim version test and add the flag if the version of Nim is new enough. Of course, if people go back and forth with choosenim, an installed wrapper might break randomly.

In the near term, the move flag can be used to move things around so that backwards compatibility is maintained. E.g. from nimui

Long term, it is preferable to avoid such complex regexes and rely on {.reorder: on.} instead.