fix hex string '0x7FFFFFFFFFFFFFFF' ToInt64() value incorrect

[yireyun]

fix hex string '0x7FFFFFFFFFFFFFFF' ToInt64() value is -0x8000000000000000, The correct value should be 9223372036854775807 (0x7FFFFFFFFFFFFFFF) .

[coveralls]

Coverage decreased (-0.03%) to 90.348% when pulling 5332d69 on yireyun:master into 7d7bc87 on yuin:master.

[coveralls]

Coverage decreased (-0.03%) to 90.348% when pulling 5332d69 on yireyun:master into 7d7bc87 on yuin:master.

[coveralls]

Coverage decreased (-0.03%) to 90.348% when pulling 5332d69 on yireyun:master into 7d7bc87 on yuin:master.

[yuin]

Lua 5.1(on 64bit environments) behaves almost same as GopherLua.

> print(string.format("%0d", tonumber("0x7FFFFFFFFFFFFFFF")))
-2147483648

[yireyun]

Note that it is not lua function tonumber () that is fixed here, but Goalng, LState.ToInt64()