This patch increases the maximum and default viewer cache size values. Due to limitations in the size of the VFS, the 80/20 texture cache/VFS split is maintained up to 5GB, then the remaining cache size is given to the texture cache. This caps the VFS size at 1GB ( up from .2 GB ).  I made corresponding changes to the XUI to allow the slider to increase to the new cache size maximum.

Bugfixes:
* The reset cache location button will no longer tell the user that the cache will be cleared if the cache is already in the default location.  Only the notification was suppressed, the cache was never cleared by this button unless the location changed.
* The reset cache location button will now correctly clear the old cache when it is reset back to the default location. 
* I fixed an order of operation programming error in an llerrs log message in the lltexturecache.cpp. This was showing wildly incorrect texture cache size during a purge.
* Code convention cleanup in llappviewer.cpp in initCache() and lltexturecache.cpp

I have built and tested on all three platforms.  The log files indicate that the caches are being initialised with the correct sizes.