Handle oveflow in O(U)String::toInt() functions
Handle oveflow in O(U)String::toInt() functions

Return 0 when overflow.
The base idea in unsigned case is checking wheather
(Max-nDigit)/nRadix < n
But for efficency, take out nDiv = Max/nRadix from loop
and corrigate it with -1 if needed.
In signed case use minimum value if the number is negativ.

Change-Id: I5b77580adbf12421b6c4b785ba9bc2a080accba2
Signed-off-by: Stephan Bergmann <05c31e1673f7a15a4f0f5429fb1e32d6e84bebe3@redhat.com>

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