Remove funcs which shlould be constants instead

The following functions have been REMOVED

    func MaxInt() int
    func MinInt() int
    func MaxUint() uint
    func UintPtrBits() int

They are now replaced by untyped constants

    MaxInt
    MinInt
    MaxUint
    UintPtrBits

Additionally one more untyped constant was added

    IntBits

This change breaks any existing code depending on the above removed
functions. They should have not been published in the first place, that
was unfortunate. Instead, defining such architecture and/or
implementation specific integer limits and bit widths as untyped
constants improves performance and allows for static dead code
elimination if it depends on these values. Thanks to minux for pointing
it out in the mail list
(https://groups.google.com/d/msg/golang-nuts/tlPpLW6aJw8/NT3mpToH-a4J).