Extend RFC3164 parser to support Cisco iOS logs

These devices seem to send non-standard logs that include a sequence
number, and a couple of extra characters (for good luck, I assume).

For example:
```
    10.51.101.233.50433 > 10.51.101.164.514: SYSLOG, length: 112 Facility local7 (23), Severity notice (5)
        Msg: 485: *Jan  8 21:50:03.406: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback100, changed state to up
```

Note the `485: *` here. This is the sequence number (and a `*` -- no
idea).

It also includes a ms-precision timestamp.

common/functions.go

@@ -3,7 +3,7 @@ package common
 import "strings"
 
 // UnsafeUTF8DecimalCodePointsToInt converts a slice containing
-// a series of UTF-8 decimal code points into their integer rapresentation.
+// a series of UTF-8 decimal code points into their integer representation.
 //
 // It assumes input code points are in the range 48-57.
 // Returns a pointer since an empty slice is equal to nil and not to the zero value of the codomain (ie., `int`).