Rename project from Lua to Lush

Binary is now 'lush', library is 'liblush.a'. Version banner shows
"Lush 0.1.0" with original Lua copyright preserved. Adds LUSH_VERSION
defines and _LUSH_VERSION global. Internal C API names, env vars, and
default paths are unchanged for upstream compatibility.

lua.c

@@ -1,6 +1,6 @@
 /*
 ** $Id: lua.c $
-** Lua stand-alone interpreter
+** Lush stand-alone interpreter
 ** See Copyright Notice in lua.h
 */
 
@@ -26,7 +26,7 @@
 
 
 #if !defined(LUA_PROGNAME)
-#define LUA_PROGNAME		"lua"
+#define LUA_PROGNAME		"lush"
 #endif
 
 #if !defined(LUA_INIT_VAR)
@@ -834,6 +834,8 @@ static int pmain (lua_State *L) {
     lua_setfield(L, LUA_REGISTRYINDEX, "LUA_NOENV");
   }
   luai_openlibs(L);  /* open standard libraries */
+  lua_pushstring(L, LUSH_VERSION);
+  lua_setglobal(L, "_LUSH_VERSION");
   createargtable(L, argv, argc, script);  /* create table 'arg' */
   lua_gc(L, LUA_GCRESTART);  /* start GC... */
   lua_gc(L, LUA_GCGEN);  /* ...in generational mode */