Add helper to escape enhanced text

[zmughal]

I have to test this some more, but this could be useful as a utility method when dealing with string interpolation:

# escapes enhanced text for Gnuplot
my $escape_enhtext = sub { shift =~ s,([{}^_@&~\\]),\\$1,gr };

[mohawk2]

Should this be an exportable utility function? I prefer not to have these issues just sit there open forever.