Release thread local storage on thread exit.

Release thread local storage on thread exit.

Calls to the EGL API from different threads may exit without releasing
their current TLS storage. This patch adds a destructor to release
them if they have not been released already. Prevents memory leakage in
processes where many threads are created.

Bug b/63434079
Bug swiftshader:80

Test: cts-tradefed run commandAndExit  cts -m CtsMediaTestCases -t \
      android.media.cts.DecodeAccuracyTest
Change-Id: I6e94a6d04ce84b884571248ab89b3b1a4e71998b
Reviewed-on: https://swiftshader-review.googlesource.com/18328
Tested-by: David Rim <davidrim@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>