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This patch ensures that we attach dbgapi to the current process as soon
as OnLoad and detach on OnUnload or process exit.

With this change:
- It is not required anymore to set HSA_ENABLE_DEBUG,
- It is now possible to enable precise memory operations (might
  be required to run the tests suite on some architectures).  The
  default test runner enables precise memory operations for this
  reason.

(imported from commit f79e8232)
(imported from commit 345b1fb1)
(imported from commit 78992eeb)
(imported from commit 1bc4f23c)
(imported from commit 91cec646)
(imported from commit dfe793f5)
(imported from commit d2a01507)

Change-Id: I21ad57fec8f42895e6d346deb49c5b834c136a2a