check if forward + displacement is positive instead of the forward alone
allow for negative strikes (down to -displacement)
ensure that strike 0 is present for bounded smile sections
fix illegal index access (which could happen for deleteArbitragePoints = true)
It seems enough to ensure that f is a valid real, so set the maximum value to QL_MAX_REAL.
If a numerical problem during interpolation occurs (zero near boundary not found or f is infinite or both)
delete the right point of the interpolation interval and try the next one. If no point is left, continue
with the extrapolation.
Merge branch 'fix20131017' into fix20131021
More ignored artifacts.
Merge pull request #43.

Allow negative forwards in Black formula as long as forward +
displacement is not negative.
Merge pull request #47.
Merge remote-tracking branch: upstream/master