Uppercases not compliant in all the book

[tzerbib]

Issue

Some functions that are quoted in the book at the beginning of sentences start with an uppercase, some others don't.
I have already made a PR to correct the ones I could correct, but for other, this is probably due to the index where all functions need to have a lowercase.
I am not sure about the fix you prefer, but I think you should add a new macro in book.mac (there is already one that enables to index a name without writing it in the book, so it is possible, using .index function and then .code Function (like you did for Tvinit in trap.t l.282-283), to have a better behavior, but then "+code" would be missing in the sidebar...)

List

I will list here all the occurrences I find in the book (July 2019).

first.t

userinit (l.608, l. 629)
scheduler (l. 759)
allocuvm (l. 882)

mem.t

main (l. 205)
mappages (l. 231)
walkpgdir (l. 253)
kalloc (l. 419)
loaduvm (l. 555)

trap.t

argint (l. 581)
argptr (l. 614)
argstr (l. 625)
trap (l. 1011)