Make improvements

- Document redbean's argon2 module
- Fix regressions in cthreads library
- Make testlib work better with threads
- Give the cthreads library lots of love
- Remove some of the stdio assembly code
- Implement getloadavg() across platforms
- Code size optimizations for errnos, etc.
- Only check for signals in main thread on Windows
- Make errnos for dup2 / dup3 consistent with posix

This change also fixes a bug in the argon2 module, where the NUL
terminator was being included in the hash encoded ascii string. This
shouldn't require any database migrations to folks who found this module
and productionized it, since the argon2 library treats it as a c string.

tool/net/largon2.c

@@ -60,14 +60,6 @@ original implementaiton.
 @release 3.0.1
 */
 
-#ifndef LUA_51
-#if !defined(LUA_VERSION_NUM) || LUA_VERSION_NUM < 502
-#define LUA_51 1
-#else
-#define LUA_51 0
-#endif
-#endif
-
 
 /***
 Argon2 hashing variants. Those fields are `userdatums`, read-only values that
@@ -350,12 +342,7 @@ largon2_hash_encoded(lua_State *L)
     encoded_len = argon2_encodedlen(t_cost, m_cost, parallelism, saltlen,
                                     hash_len, variant);
 
-#if LUA_51
-    luaL_buffinit(L, &buf);
-    encoded = luaL_prepbuffer(&buf);
-#else
     encoded = luaL_buffinitsize(L, &buf, encoded_len);
-#endif
 
     if (variant == Argon2_d) {
         ret_code =
@@ -373,12 +360,7 @@ largon2_hash_encoded(lua_State *L)
                                salt, saltlen, hash_len, encoded, encoded_len);
     }
 
-#if LUA_51
-    luaL_addsize(&buf, encoded_len);
-    luaL_pushresult(&buf);
-#else
-    luaL_pushresultsize(&buf, encoded_len);
-#endif
+    luaL_pushresultsize(&buf, encoded_len - 1);
 
     if (ret_code != ARGON2_OK) {
         err_msg = (char *) argon2_error_message(ret_code);
@@ -484,30 +466,6 @@ largon2_push_argon2_variants_table(lua_State *L)
 }
 
 
-#if LUA_51
-/* Compatibility for Lua 5.1.
- *
- * luaL_setfuncs() is used to create a module table where the functions have
- * largon2_config_t as their first upvalue. Code borrowed from Lua 5.2 source. */
-static void
-compat_luaL_setfuncs(lua_State *l, const luaL_Reg *reg, int nup)
-{
-    int i;
-
-    luaL_checkstack(l, nup, "too many upvalues");
-    for (; reg->name != NULL; reg++) { /* fill the table with given functions */
-        for (i = 0; i < nup; i++)      /* copy upvalues to the top */
-            lua_pushvalue(l, -nup);
-        lua_pushcclosure(l, reg->func, nup); /* closure with those upvalues */
-        lua_setfield(l, -(nup + 2), reg->name);
-    }
-    lua_pop(l, nup); /* remove upvalues */
-}
-#else
-#define compat_luaL_setfuncs(L, l, nup) luaL_setfuncs(L, l, nup)
-#endif
-
-
 static const luaL_Reg largon2[] = { { "verify", largon2_verify },
                                     { "hash_encoded", largon2_hash_encoded },
                                     { "t_cost", largon2_cfg_t_cost },
@@ -524,7 +482,7 @@ luaopen_argon2(lua_State *L)
     lua_newtable(L);
 
     largon2_create_config(L);
-    compat_luaL_setfuncs(L, largon2, 1);
+    luaL_setfuncs(L, largon2, 1);
 
     /* push argon2.variants table */