A texture's base level can be any positive integer, but SwiftShader
stores texture levels in a array that has an implementation
dependent size (IMPLEMENTATION_MAX_TEXTURE_LEVELS). To avoid
accessing this array out of bounds, a class was added to make sure
all accesses to the array are done within its bounds.

Change-Id: I9b439018f209a47371bd2959ba847345326964dd
Reviewed-on: https://swiftshader-review.googlesource.com/20488Tested-by: Alexis Hétu <sugoi@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>