[patch] REXML::Formatters::Pretty#wrap fails on long words and on long lines

[alk]

I encountered bug in REXML by running rcov which uses pretty formatter for it's html reports.

It turns out that #wrap fails with too long words. In this case rindex returns nil, which is not accounted for.

Another issue is recursion. I've run into stack overflow. The fix is (hopefuly) equivalent transformation of recursive computational process into interative.