error.h: add missing includes

[matdibu]

these missing headers are needed since this header contains code

[frozencemetery]

What problem is this fixing?

[matdibu]

It's just a technicality:

• in theory, it would be nice if the header included its dependencies
• in practice, the lack of includes confused my IDE

[frozencemetery]

It's been several months; closing as inactive.