curl: detect and bail out early on parameter integer overflows

[bagder]

Make the number parser aware of the maximum limit curl accepts for a
value and return an error immediately if larger, instead of running an
integer overflow later.

Fixes #1730

[mention-bot]

@bagder, thanks for your PR! By analyzing the history of the files in this pull request, we identified @yangtse, @captain-caveman2k and @kdudka to be potential reviewers.

[coveralls]

Coverage increased (+0.08%) to 75.356% when pulling f1c26ef on bagder/curl-integer-overflow-1730 into d6c8def on master.

[coveralls]

Coverage increased (+0.06%) to 75.33% when pulling 2f97b7f on bagder/curl-integer-overflow-1730 into d6c8def on master.