[PATCH 1/6] [DJGPP] libstdc++-v3/config/os/djgpp/error_constants.h: Update according to errno codes available for DJGPP

[DJ Delorie]

> I can't really judge this one.  Either DJ or Jon would need to some in 
> on this.

Looks OK to me, although in the default configuration (plain DJGPP)
the #ifdefs will always be false (omitted), which is harmless.