Ipopt v1.11.0

Diff since v1.10.6

Merged pull requests:

• Update README.md for libHSL (#497) (@amontoison)
• Support Ipopt 3.14.19 (#498) (@amontoison)
• Add show(::IO, ::_VectorNonlinearOracle) (#501) (@odow)
• Add timers to _VectorNonlinearOracle (#502) (@odow)
• Prep for v1.11.0 (#503) (@odow)