lua: Migrate to gentargets and improve it

Closes #803

Based on initial patch by rvpaasen@t3i.nl

[Peter: lua/luac needs liblua.so.* on target]
Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/lua/lua-gc_performance.patch

@@ -0,0 +1,14 @@
+--- lua-5.1.4.orig/src/llex.c	2007/12/28 15:32:23	2.63.1.3
++++ lua-5.1.4/src/llex.c	2010/02/23 12:36:59
+@@ -118,8 +118,10 @@
+   lua_State *L = ls->L;
+   TString *ts = luaS_newlstr(L, str, l);
+   TValue *o = luaH_setstr(L, ls->fs->h, ts);  /* entry for `str' */
+-  if (ttisnil(o))
++  if (ttisnil(o)) {
+     setbvalue(o, 1);  /* make sure `str' will not be collected */
++    luaC_checkGC(L);
++  }
+   return ts;
+ }
+