Implement printf, dprintf, string.format

Docs/Lua-String-Formatting.md

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+# Lua String Formatting
+
+Lua contains a builtin routine, string.format, which is similar to "printf."
+We have reimplemented this from scratch, adding a bunch of new formatting
+directives.
+
+We have also added formatting routines that output to the
+console and the debug logs.  The new routines are:
+
+format(format_string, arg1, arg2, arg3...)
+dformat(format_string, arg1, arg2, arg3...)
+