I just tried this "easter egg" on the latest version of MacVim. Pretty cool.
It appears also to be a tribute the the Hitchhiker's Guide to the Galaxy. Also, If you search help by typing ":help smile", it says "You found it, Arthur! holy-grail", a reference to Arthur Dent.
Is it typical vim style to use a space after # in C files? That seems like a lot of unnecessary churn in the first file.
[edit] Aaand I'm embarrassed about having made the first comment a negative one. D'oh. But, I do like the Cosmic Cutie! Even if Douglas Adams didn't. Funny patch, yes.
That's not the problem. The problem is the person making the PR projecting their own style choices instead of following the project's. They explicitly changed other contributors' code in a negative (stylistic) way.
The space following the "#" is meant to signify that the preprocessor directive is nested one layer deep. You can see that this style is used in other files, like here: https://github.com/vim/vim/blob/master/src/gui.c#L40-L42
So no, I think this is Bram bringing one file's indentation style in line with the rest of the project.