SST Beta 0.19 (a.k.a. Solving Spurious Terribleness)

This one took a little longer than hoped but gave us the chance to cram
in a few more things than expected too.

New stuff this time around:

* Added a fix for the dreaded "No Steam Logon" error in Left 4 Dead 1
  and 2 (thanks aciidz and bill for doing all the hard work on that!)

* Improved sst_speedrun_start to simply append an additional number if
  the demo already exists, rather than failing to record.

* Fixed a regression in the last update that would crash when reloading
  the plugin if the rinput feature was active

* Fixed the L4D1 demo compatibility feature (also a regression last
  update; oops!)

* Extended Portal colour customisation to the current SteamPipe build.

Thanks, and have fun! :^)