dot and other regex chars in namespace cause unexpected results

[zacronos]

Currently, enabling namespaces which contain regex special characters leads to unexpected results. Examples:

var debug = require('debug');
debug.enable("abc[def],x.z,what?");

console.log(debug.enabled('abcf'));  // yields true, should be false
console.log(debug.enabled('abc[def]'));  // yields false, should be true

console.log(debug.enabled('xyz'));  // yields true, should be false

console.log(debug.enabled('what?'));  // yields false, should be true
console.log(debug.enabled('wha'));  // yields true, should be false

debug.enable("oops[");  // throws an error

I've submitted a PR which handles this by escaping regex special characters other than *: #250

[zacronos]

PR to fix this is merged, thanks!