Use raw strings for regexes; fixes SyntaxWarning: invalid escape sequence

[dlitz]

When running gw --help for the first time under Python 3.12, I get a bunch of warnings:

.../src/greaseweazle/tools/util.py:103: SyntaxWarning: invalid escape sequence '\d'
  m = re.match('(\d*\.\d+|\d+)rpm', arg)
.../src/greaseweazle/tools/util.py:106: SyntaxWarning: invalid escape sequence '\d'
  m = re.match('(\d*\.\d+|\d+)ms', arg)
.../src/greaseweazle/tools/util.py:109: SyntaxWarning: invalid escape sequence '\d'
  m = re.match('(\d*\.\d+|\d+)us', arg)
.../src/greaseweazle/tools/util.py:112: SyntaxWarning: invalid escape sequence '\d'
  m = re.match('(\d*\.\d+|\d+)ns', arg)
.../src/greaseweazle/tools/util.py:115: SyntaxWarning: invalid escape sequence '\d'
  m = re.match('(\d*\.\d+|\d+)scp', arg)
.../src/greaseweazle/tools/util.py:193: SyntaxWarning: invalid escape sequence '\d'
  m = re.match('(\d+)(-(\d+)(/(\d+))?)?$', crange)
.../src/greaseweazle/tools/util.py:220: SyntaxWarning: invalid escape sequence '\d'
  m = re.match('([+-]\d+)$', v)
.../src/greaseweazle/tools/util.py:224: SyntaxWarning: invalid escape sequence '\d'
  m = re.match('1/(\d+)$', v)
  info        Display information about the Greaseweazle setup.
.../src/greaseweazle/codec/codec.py:217: SyntaxWarning: invalid escape sequence '\s'
  '\s+([\w,.-]+)', t)
.../src/greaseweazle/codec/codec.py:236: SyntaxWarning: invalid escape sequence '\.'
  '(?:\.([01]))?', x)
.../src/greaseweazle/codec/codec.py:264: SyntaxWarning: invalid escape sequence '\s'
  '\s*([a-zA-Z0-9:,._-]+)', t)
.../src/greaseweazle/codec/codec.py:283: SyntaxWarning: invalid escape sequence '\s'
  '\s*([a-zA-Z0-9:,._*-]+)', t)

This doesn't happen when loading the cached .pyc files, so to reproduce the original problem, remove the __pycache__ directories before running gw.

This pull request fixes these errors by using raw strings (r'foo\d' instead of 'foo\d').