use error.h *only if it exists*

[dgeo]

fixes #117

[dhawes]

This is effectively the same as just removing the #include.

That may be the correct solution here, as error.h does seem to be unused. I wonder if errno.h was intended?

[dotmjs]

Is "#ifdev" a mistake (should be "#ifdef")? How did this successfully compile ?

[dgeo]

Of course !
Sorry, I'm not sure how it happened, i don't have it in my original "patch" :(

[dgeo]

Can/will this be integrated ?

[dhawes]

In its current state I would not merge this for the reason I hinted at in my comment: adding that #ifdef with no other changes effectively just removes the #include.

I'd like to see analysis to determine if this should be errno.h now or simply be removed, and if this has always been the case or if something changed at some point.