Remove extern/replace.h

This was really only necessary for using the internal talloc library,
but it turns out that wasn't portable at all.  This fixes the problem
by manually defining the few cases where talloc actually used that
auto-generated header, which was causing troubles for people on
non-Linux systems.
Make it harder to use an internal talloc

This provides a strong warning message to users who try and use their
own internal talloc library, as it's probably not a good idea.
Package managers are a Good Thing :).
Run chkindent on extern/talloc.c

Looks like I forgot to run this before committing... whoops!
texstrip: Fix ^\documentclass[*$

I accidentally checked for '\documentclass{', which breaks when there
are options to the document class.  You'll have to "make clean" to fix
this bug, but it shouldn't be a real problem because it didn't even
work before.