pkg/lua: add download and build of lua as pkg

- download of v5.3.4 of Lua from git
- building using RIOT build system
- patched to remove the need for _times and _link to be
provided to Lua via newlib.

pkg/lua/Makefile

@@ -0,0 +1,12 @@
+PKG_NAME=lua
+PKG_URL=https://github.com/lua/lua.git
+PKG_VERSION=e354c6355e7f48e087678ec49e340ca0696725b1
+PKG_LICENSE=MIT
+
+.PHONY: all
+
+all:
+	@cp Makefile.lua $(PKG_BUILDDIR)
+	"$(MAKE)" -C $(PKG_BUILDDIR) -f Makefile.lua
+
+include $(RIOTBASE)/pkg/pkg.mk

pkg/lua/Makefile.include

@@ -0,0 +1 @@
+INCLUDES += -I$(PKGDIRBASE)/lua

pkg/lua/Makefile.lua

@@ -0,0 +1,9 @@
+SRC := $(filter-out lua.c luac.c,$(wildcard *.c))
+
+# This builds for native using POSIX system calls and some extra libraries, and
+# removes a compiler warning that warns against using tmpnam().
+ifeq ($(BOARD),native)
+  CFLAGS += -DLUA_USE_LINUX
+endif
+
+include $(RIOTBASE)/Makefile.base

pkg/lua/doc.txt

@@ -0,0 +1,6 @@
+/**
+ * @defgroup pkg_lua Lua ported to RIOT
+ * @ingroup  pkg
+ * @brief    Provides Lua support for RIOT
+ * @see      https://github.com/lua/lua
+ */

pkg/lua/patches/0001-Remove-dependency-on-nonexistent-RIOT-syscalls.patch

@@ -0,0 +1,62 @@
+From b681cb20ee6bfc31b8ba23ec321140aae6e53e9d Mon Sep 17 00:00:00 2001
+From: danpetry <daniel.petry@fu-berlin.de>
+Date: Wed, 23 May 2018 14:09:17 +0200
+Subject: [PATCH 1/1] Remove dependency on nonexistent RIOT syscalls
+
+Os.rename and os.clock, in Lua, now always return an error message.
+Also, l_randomizePivot, which is used by table.sort, will always
+supply 0 rather than a pseudorandom number.
+---
+ loslib.c  | 7 ++-----
+ ltablib.c | 4 +++-
+ 2 files changed, 5 insertions(+), 6 deletions(-)
+
+diff --git a/loslib.c b/loslib.c
+index dd2bb378..f9e5cbd2 100644
+--- a/loslib.c
++++ b/loslib.c
+@@ -157,9 +157,7 @@ static int os_remove (lua_State *L) {
+ 
+ 
+ static int os_rename (lua_State *L) {
+-  const char *fromname = luaL_checkstring(L, 1);
+-  const char *toname = luaL_checkstring(L, 2);
+-  return luaL_fileresult(L, rename(fromname, toname) == 0, NULL);
++  return luaL_error(L, "This function is not implemented in RIOT yet");
+ }
+ 
+ 
+@@ -181,8 +179,7 @@ static int os_getenv (lua_State *L) {
+ 
+ 
+ static int os_clock (lua_State *L) {
+-  lua_pushnumber(L, ((lua_Number)clock())/(lua_Number)CLOCKS_PER_SEC);
+-  return 1;
++  return luaL_error(L, "This function is not implemented in RIOT yet");
+ }
+ 
+ 
+diff --git a/ltablib.c b/ltablib.c
+index 588bf40d..8895b653 100644
+--- a/ltablib.c
++++ b/ltablib.c
+@@ -235,13 +235,15 @@ static int unpack (lua_State *L) {
+ /* type for array indices */
+ typedef unsigned int IdxT;
+ 
+-
+ /*
+ ** Produce a "random" 'unsigned int' to randomize pivot choice. This
+ ** macro is used only when 'sort' detects a big imbalance in the result
+ ** of a partition. (If you don't want/need this "randomness", ~0 is a
+ ** good choice.)
+ */
++
++#define l_randomizePivot() 0
++
+ #if !defined(l_randomizePivot)		/* { */
+ 
+ #include <time.h>
+-- 
+2.17.0
+