validate: try multiple exploits for poly vulns

[davisjam]

Problem: The detectors are eager to exploit higher-order polynomially vulnerable regexes.

In doing so they may overstep and cause a match, so no backtracking is required.

Example: See discussion in Weideman: https://github.com/NicolaasWeideman/RegexStaticAnalysis/issues/11

Solution: In such a case the lesser polynomials may still be effective. validate-vuln.pl now iterates over the proposed list of pumpPairs and tries pumpPairs 1..$i. If any time out we have a winner.

Fixes: #40

Test:

• Various tests for check-regex

Misc:

• Also fixes issue in check-regex: wrong path to cache-client