Add AIThreadID - Cleanup of apr_os_thread* related code.

Apart from just really cleaning things up and moving
everything into one class regarding thread IDs (ie,
is_main_thread(), comparing ID's etc), this also
fixes an obscure bug where LL was casting thread ID's
to U32 and then compared those to find out if it
the same thread. It's theoretically possible that
such fails on a 64bit OS.

By generalizing the interface, I adopted the use
of a thread-local cache for the current thread ID
as used by LLMutex et al, so now all code benefits
from that. The idea was even extended to now also
be used for is_main_thread() tests and even resetting
a thread ID to the ID of the current thread.

indra/llcommon/llaprpool.h

@@ -62,22 +62,22 @@ class LL_COMMON_API LLAPRPool
 protected:
 	apr_pool_t* mPool;			//!< Pointer to the underlaying pool. NULL if not initialized.
 	LLAPRPool* mParent;			//!< Pointer to the parent pool, if any. Only valid when mPool is non-zero.
-	apr_os_thread_t mOwner;		//!< The thread that owns this memory pool. Only valid when mPool is non-zero.
+	AIThreadID mOwner;			//!< The thread that owns this memory pool. Only valid when mPool is non-zero.
 
 public:
 	//! Construct an uninitialized (destructed) pool.
-	LLAPRPool(void) : mPool(NULL) { }
+	LLAPRPool(void) : mPool(NULL), mOwner(AIThreadID::none) { }
 
     //! Construct a subpool from an existing pool.
 	// This is not a copy-constructor, this class doesn't have one!
-	LLAPRPool(LLAPRPool& parent) : mPool(NULL) { create(parent); }
+	LLAPRPool(LLAPRPool& parent) : mPool(NULL), mOwner(AIThreadID::none) { create(parent); }
 
 	//! Destruct the memory pool (free all of it's subpools and allocated memory).
 	~LLAPRPool() { destroy(); }
 
 protected:
 	// Create a pool that is allocated from the Operating System. Only used by LLAPRRootPool.
-	LLAPRPool(int) : mPool(NULL), mParent(NULL), mOwner(apr_os_thread_current())
+	LLAPRPool(int) : mPool(NULL), mParent(NULL)
 	{
 		apr_status_t const apr_pool_create_status = apr_pool_create(&mPool, NULL);
 		llassert_always(apr_pool_create_status == APR_SUCCESS);
@@ -104,7 +104,7 @@ public:
 	apr_pool_t* operator()(void) const
 	{
 		llassert(mPool);
-		llassert(apr_os_thread_equal(mOwner, apr_os_thread_current()));
+		llassert(mOwner.equals_current_thread());
 		return mPool;
 	}
 
@@ -112,7 +112,7 @@ public:
 	void clear(void)
 	{
 		llassert(mPool);
-		llassert(apr_os_thread_equal(mOwner, apr_os_thread_current()));
+		llassert(mOwner.equals_current_thread());
 		apr_pool_clear(mPool);
 	}
 
@@ -124,13 +124,13 @@ public:
 	void* palloc(size_t size)
 	{
 		llassert(mPool);
-		llassert(apr_os_thread_equal(mOwner, apr_os_thread_current()));
+		llassert(mOwner.equals_current_thread());
 		return apr_palloc(mPool, size);
 	}
 	void* pcalloc(size_t size)
 	{
 		llassert(mPool);
-		llassert(apr_os_thread_equal(mOwner, apr_os_thread_current()));
+		llassert(mOwner.equals_current_thread());
 		return apr_pcalloc(mPool, size);
 	}
 #endif