Avoid pathname errors, implement `*server-boot-hooks*`, formatting improvements.

[defaultxr]

Hi. This PR has 3 relatively minor changes:

• Avoid errors when testing for files whose names contain CL pathname wildcards.

For example, if a file /Users/user/huh?.txt exists, (probe-file "/Users/user/huh?.txt") will give an error.

I added file-exists-p which does not have this issue, and fixed full-pathname as well.

• Implement *server-boot-hooks*.

This is mostly for consistency with *server-quit-hooks*.

• Minor formatting improvements.

Mostly indentation and the like, but also a few minor code changes to improve clarity/consistency.

[byulparan]

(sc::full-pathname "~/Desktop/foo.txt") is not convert full-pathname. so I was some improve it. 738937c9f762cdc32ff5cc2eb0ba2dc5eb9b7a14