A rollup of several improvements

Since the last release:

• collecting has, finally, become a shim for with-collectors which was long overdue;
• there are general accumulators by with-accumulators, which are quite powerful;
• binding has bind/macro for macrolet;
• local functions and macros bound by binding themselves implicitly use binding;
• bind/values will ignore nil allowing you to skip some values;
• there is a new hack, stringtable which is a simple readtable for strings;
• there are some other improvements which shouldn't involve new or repaired functionality.

The documentation should correspond to what exists: in particular all of the new things above are described.