#115297: Speeding up setPairs(theSameType) by use of LinkedHashSet instead of ArrayList

sigtest .sig files generated for all modules with some packages being public or friend. The sigtest generally complained a lot about 'hidden classes' - e.g. classes that are shown in a signature of a visible method, but are not itself visible at all. I have modified such methods to be package private. Some modules have tons of such APIs (especially library wrappers), for them I have disabled the check by adding sigtest.gen.fail.on.error=false. Some modules causes the current version of sigtestdev.jar to fail with NPE, for them I have disabled the fail on error as well. The whole check can be executed with ant -f nbbuild/build.xml gen-sigtests -Dsigtest.jar=the_path_to_jar_that_jtulach_netbeans_org can sent you, as it does not seem to be opensourced yet

#112691: Cannot fix 112691 as the exception reporter looses message from exceptions

Add sigtests files for latests bits

Trying to find out who calls HelpCtx in the NotifyLaterTest from core/windows

#103300: Improving javadoc

#104806: Additional fix, by making the ExcludingLookup result listening using a weak listener

#112574: Under concurent access it is not possible to guarantee a state of cache after exiting the synchronized block - let's remove the assert, it was apperently wrong

Fixing warnings.

#101103: Prevent document leak by not reusing DOM parsers. reset() is flawed aand there's no reliable way around it. Test included for the brave that would like the cache back.