10x speedup to "c" method for XVectorList objects

git-svn-id: https://hedgehog.fhcrc.org/bioconductor/trunk/madman/Rpacks/IRanges@75843 bc3139a8-67e5-0310-9ffc-ced21a209358
add reminder

git-svn-id: https://hedgehog.fhcrc.org/bioconductor/trunk/madman/Rpacks/IRanges@75844 bc3139a8-67e5-0310-9ffc-ced21a209358
adding new IntervalTree code
some polish of code and comments

git-svn-id: https://hedgehog.fhcrc.org/bioconductor/trunk/madman/Rpacks/IRanges@75845 bc3139a8-67e5-0310-9ffc-ced21a209358
Merge branch 'local-hedgehog'
Merge branch 'master' of https://github.com/hcorrada/IRanges