Remove integer keys from lush table, use string lookups (issue #29)

VM now resolves lush functions via luaH_getshortstr through interned
TString pointers, so wrapping lush.command = my_wrapper is transparently
picked up. The lush table no longer has integer-keyed duplicates.

lcmd.h

@@ -8,6 +8,7 @@
 #define lcmd_h
 
 #include "lua.h"
+#include "lobject.h"
 
 /* OP_LUSH sub-operation indices (B operand selects which function) */
 #define LUSH_OP_COMMAND      0
@@ -23,6 +24,8 @@ int lushCmd_getenv (lua_State *L);
 int lushCmd_setenv (lua_State *L);
 int lushCmd_subcmd (lua_State *L);
 
+extern TString *lushname[];
+
 LUAMOD_API int luaopen_lush (lua_State *L);
 
 #endif