pip install now uses --target and --install-scripts instead of --prefix since the latter is not available on ancient versions of pip.

Use full bin path names when executing grumpy tools. Otherwise some invocations fail with "no such file or directory" on Make 3.81 on OS X.

Simplify dispatch and block body logic. Eliminate Block type. Unify functions with and without a dispatch function. Now only generators need a closure for holding state since the dispatcher is in a loop instead of an inner function.