Revert "Load all functions when loading a libphutil library"

Summary:
This reverts commit 3475788eddcace2eb71665a50565d74deaef62e0.

We can't do this without doing more comprehensive changes at the same time. There are two problems:

• We may load some function which, e.g., does "new X()" in its implementation, triggering an include of a module which defines class X. This class may extend a class in another library which hasn't loaded yet. We could fix this problem by ignoring phutil_require_module() during function autoload, but can't fix the next one.
• We may load some function which is defined in a module which also defines some class X, which extends a class in another library which hasn't loaded yet.

We need to wait to land this to avoid triggering these problems.

Test Plan: Strict revert.

Reviewers: nh, vrana, btrahan

Reviewed By: nh

CC: aran

Maniphest Tasks: T1103

Differential Revision: https://secure.phabricator.com/D2556