#3 Makefile top-level target canonicalization

[Warren Young]

The current makefile mixes the actions of "all", "check" and "clean" in ways that violate my expectations. The attached patch fixes the following problems:

1. "make ; make" no longer builds the test programs twice
2. -Werror is no longer the default build: you have to ask for it with "make check-werror"
3. redundant targets are collected together

All of this is a matter of taste, so I won't be upset if you don't apply this patch entirely. The items are ordered most important first, by my lights.

[Jonathan Wakely]

Looks good to me.

[Jonathan Wakely]

Committed as d7227d867284c6a4cae47fa1b691348394e85728 - thanks!