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.

Various changes toward getting tracebacks working. Frame objects now hold the block they are running. Populate lineno field for frame objects. Expose some fields such as f_lineno to Python.