Avoid 14 bit integer overflow in clockseq

[ctavan]

I just got the quite unlikely case of a clockseq overlow:

$ node test/test.js 
Pass: uuids with current time have expected order
Pass: uuids with time option have expected order
Pass: IDs created at same msec are different
Fail: IDs created at same 100 nsec throw an error
Pass: IDs created at t and t - 100ns have different clockseq
Pass: Explicit options produce expected id
Pass: 1ns separation between adjacent uuids
Pass: Short parse
Pass: Dirty parse

Sanity check 10000 v1 uuids

node.js:201
        throw e; // process.nextTick error, or 'error' event on first tick
              ^
Error: 5470a8a0-2a5d-11e1-c000-7938e6977d1e is not a valid UUID string
    at Error (unknown source)
    at Object.<anonymous> (/****/node-uuid/test/test.js:157:13)
    at Module._compile (module.js:432:26)
    at Object..js (module.js:450:10)
    at Module.load (module.js:351:31)
    at Function._load (module.js:310:12)
    at Array.0 (module.js:470:10)
    at EventEmitter._tickCallback (node.js:192:40)

The clock-seq-part is c000 which is invalid. Apparently we got an overflow from 0x3fff to 0x4000 of the clockseq here.

I tried to write a test to catch this, but it's currently not possible since we cannot control the _seedBytes from the outside. Still I think my patch should fix this.

Sorry, that there's some other old stuff in the commit range, I don't really get it how to keep that out of here....

[broofa]

Good catch, btw. Sorry I didn't merge this before now - 'Been really busy with work and holiday stuff.