Running of automatically generated Lua programs sometimes failed
with an error "'<name>' expected near 'and'" (0.07%).

Example of the error is the following:

```lua
local t = {}
t.or = 0  -- "'<name>' expected near 'or'"
t.nil = 0 -- "'<name>' expected near 'nil'"
t.not = 0 -- "'<name>' expected near 'not'"
```

This error was caused by reserved Lua keywords used as table indices.
The patch fixes serializer, if the automatically generated index
name is equal to the reserved keyword then postfix "_1" is added
to index name.

NO_CHANGELOG=testing
NO_DOC=testing
NO_TEST=testing