Fix some warnings with GCC -Wall

library/Core.cpp

@@ -300,12 +300,6 @@ static void listScripts(PluginManager *plug_mgr, std::map<string,string> &pset,
     }
 }
 
-static bool fileExists(std::string path)
-{
-    ifstream script(path.c_str());
-    return script.good();
-}
-
 namespace {
     struct ScriptArgs {
         const string *pcmd;
@@ -1612,16 +1606,19 @@ bool Core::Init()
         cerr << "Starting IO thread.\n";
         // create IO thread
         thread * IO = new thread(fIOthread, (void *) temp);
+        (void)IO;
     }
     else
     {
         cerr << "Starting dfhack.init thread.\n";
         thread * init = new thread(fInitthread, (void *) temp);
+        (void)init;
     }
 
     cerr << "Starting DF input capture thread.\n";
     // set up hotkey capture
     thread * HK = new thread(fHKthread, (void *) temp);
+    (void)HK;
     screen_window = new Windows::top_level_window();
     screen_window->addChild(new Windows::dfhack_dummy(5,10));
     started = true;
@@ -1819,6 +1816,7 @@ void Core::Resume()
     lock_guard<mutex> lock(d->AccessMutex);
 
     assert(d->df_suspend_depth > 0 && d->df_suspend_thread == tid);
+    (void)tid;
 
     if (--d->df_suspend_depth == 0)
         d->core_cond.Unlock();
@@ -1858,6 +1856,7 @@ void Core::DisclaimSuspend(int level)
     lock_guard<mutex> lock(d->AccessMutex);
 
     assert(d->df_suspend_depth == level && d->df_suspend_thread == tid);
+    (void)tid;
 
     if (level == 1000000)
         d->df_suspend_depth = 0;

library/DataDefs.cpp

@@ -271,8 +271,6 @@ virtual_identity *virtual_identity::find(void *vtable)
     Core &core = Core::getInstance();
     std::string name = core.p->doReadClassName(vtable);
 
-    virtual_identity *actual = NULL;
-
     auto name_it = name_lookup.find(name);
     if (name_it != name_lookup.end()) {
         virtual_identity *p = name_it->second;

library/LuaApi.cpp

@@ -2243,7 +2243,7 @@ static int filesystem_listdir(lua_State *L)
         return 3;
     }
     lua_newtable(L);
-    for(int i=0;i<files.size();i++)
+    for(size_t i=0;i<files.size();i++)
     {
         lua_pushinteger(L,i+1);
         lua_pushstring(L,files[i].c_str());
@@ -2492,7 +2492,7 @@ static int internal_patchBytes(lua_State *L)
     {
         uint8_t *addr = (uint8_t*)checkaddr(L, -2, true);
         int isnum;
-        uint8_t value = (uint8_t)lua_tounsignedx(L, -1, &isnum);
+        lua_tounsignedx(L, -1, &isnum);
         if (!isnum)
             luaL_error(L, "invalid value in write table");
         lua_pop(L, 1);

library/LuaTools.cpp

@@ -953,6 +953,7 @@ bool DFHack::Lua::SafeCallString(color_ostream &out, lua_State *state, const std
         env_idx = lua_absindex(state, env_idx);
 
     int base = lua_gettop(state);
+    (void)base; // used in assert()
 
     // Parse the code
     if (luaL_loadbuffer(state, code.data(), code.size(), debug_tag) != LUA_OK)

library/LuaTypes.cpp

@@ -911,6 +911,7 @@ static int method_container_insert(lua_State *state)
 static int meta_bitfield_len(lua_State *state)
 {
     uint8_t *ptr = get_object_addr(state, 1, 0, "get size");
+    (void)ptr;
     auto id = (bitfield_identity*)lua_touserdata(state, UPVAL_CONTAINER_ID);
     lua_pushinteger(state, id->getNumBits());
     return 1;

library/LuaWrapper.cpp

@@ -46,8 +46,6 @@ distribution.
 using namespace DFHack;
 using namespace DFHack::LuaWrapper;
 
-static luaL_Reg no_functions[] = { { NULL, NULL } };
-
 /**
  * Report an error while accessing a field (index = field name).
  */
@@ -1594,8 +1592,6 @@ static void RenderTypeChildren(lua_State *state, const std::vector<compound_iden
 
 static int DoAttach(lua_State *state)
 {
-    int base = lua_gettop(state);
-
     lua_newtable(state);
     lua_rawsetp(state, LUA_REGISTRYINDEX, &DFHACK_PTR_IDTABLE_TOKEN);
 

library/PluginManager.cpp

@@ -184,8 +184,8 @@ struct Plugin::LuaEvent : public Lua::Event::Owner {
 
 Plugin::Plugin(Core * core, const std::string & path,
     const std::string &name, PluginManager * pm)
-    :name(name),
-     path(path),
+    :path(path),
+     name(name),
      parent(pm)
 {
     plugin_lib = 0;
@@ -492,7 +492,6 @@ command_result Plugin::invoke(color_ostream &out, const std::string & command, s
 
 bool Plugin::can_invoke_hotkey(const std::string & command, df::viewscreen *top )
 {
-    Core & c = Core::getInstance();
     bool cr = false;
     access->lock_add();
     if(state == PS_LOADED)