lua: fix HTTP loadstring in lua 5.2+

Close #14988
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

share/lua/intf/http.lua

@@ -55,6 +55,14 @@ function escape(s)
     return (string.gsub(s,"([%^%$%%%.%[%]%*%+%-%?])","%%%1"))
 end
 
+function my_vlc_load(code, filename)
+    if _VERSION == "Lua 5.1" then
+        return loadstring(code, filename)
+    else
+        return load(code, filename)
+    end
+end
+
 function process_raw(filename)
     local input = io.open(filename):read("*a")
     -- find the longest [===[ or ]=====] type sequence and make sure that
@@ -77,7 +85,7 @@ function process_raw(filename)
     io.write("\n")
     end
     --]]
-    return assert(loadstring(code,filename))
+    return assert(my_vlc_load(code,filename))
 end
 
 function process(filename)

share/lua/modules/sandbox.lua

@@ -34,7 +34,6 @@ local sandbox_blacklist = {
     getmetatable = true,
     load = true, -- Can be protected I guess
     loadfile = true, -- Can be protected I guess
-    loadstring = true, -- Can be protected I guess
     rawequal = true,
     rawget = true,
     rawset = true,
@@ -46,6 +45,10 @@ local sandbox_blacklist = {
     debug = true,
 }
 
+if _VERSION == "Lua 5.1" then
+    sandbox_blacklist["loadstring"] = true
+end
+
 function readonly_table_proxy(name,src,blacklist)
     if type(src)=="nil" then return end
     if type(src)~="table" then error("2nd argument must be a table (or nil)") end