This resolves #180.
This script was only profiling the first screenful of text from the source file. Now it scrolls through and highlights the entire file. The profiling report still depends on the (terminal) window size. A larger window size results in fewer page scrolls and less work for Vim (fewer matches in the report).
This replaces the inefficient match for the Pod type name after =end, which was attempted at the start of every line. Instead, we use 'nextgroup' after every delimited Pod region. When highlighting t_source/perl6/basic.t, this pattern was the 2nd most costly in terms of time spent, despite it never even successfully matching in that file, so this is a nice performance boost.
Running "make install" will now remove the regex optimization from the syntax file if the user has an old Vim. For those who try to run an unmodified perl6.vim, we now print an error when the syntax file is loaded.