cpan.bbclass: matches more lines

cpan.bbclass: matches more lines

Fixed:
- There might be a space between "#!" and "/pat/to/usr/bin/perl", e.g.:
  "#! /usr/bin/perl", now also matches it.

- There might be the lines like the following in the body:
  eval 'exec /path/to/usr/bin/perl-native/perl -S $0 ${1+"$@"}'

  Now we only check "#! */path/to/usr/bin/perl" to make sure it is a
  perl script, but match and fix the lines in both header and body.

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>