Lua :
Lua :

This patch changes LuaNil PMC, it used to be a singleton, this patch makes it a normal PMC.
some other methods are implemented for morphing into other Lua types (LuaString, LuaNumber, LuaBoolean).

Courtesy of Klaas-Jan Stol.

+ change Parrot_PMC_typenum by pmc_type

git-svn-id: 6e74a02f85675cec270f5d931b0f6998666294a3@11205 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

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