Casting function pointers to different types

I noticed in a recent code review that we are casting function pointers to functions with different types in. For example:

https://github.com/wiredtiger/wiredtiger/blob/develop/src/cursor/cur_std.c#L55

I did some digging, and it appears that doing so is undefined according to the C99 standard. See: http://stackoverflow.com/questions/559581/casting-a-function-pointer-to-another-type

On the other hand it is used by a bunch of common system libraries, so the expectation is that it will work.