git-http-fetch: not a builtin

git-http-fetch: not a builtin

This splits up git-http-fetch so that it isn't built-in.

It also removes the general dependency on curl, because it is no
longer used by any built-in code. Because they are no longer LIB_OBJS,
add LIB_H to the dependencies of http-related object files, and remove
http.h from the dependencies of transport.o

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>