Fixed crash on mutex destroy.

 * Added some checks in `axis2_op_ctx_destroy_mutex` funtion.
 * Check allocator in `axutil_thread_mutex_destroy` function.
 * Check if allocator is correct in _create functions in
   `thread_unix.c` file.

 Sometimes allocator is invalid. So we should check if allocator
 is correct to prevent segmentation faults in future.
Fixed crashes on srteam write.

 * Added check if stream and stream->buffer are not NULLs in
   `axutil_stream_write_basic` function.

 Sometimes stream->buffer is NULL. This causes segfault in
 memcpy function.
Fixed segmentation faults on wrong allocator.

 * Redefined `AXIS2_CHECK_ENV` macro.
 * Added `AXIS2_ENV_CHECK_VOID` macro.
 * Replaced `AXIS2_ENV_CHECK(env, void)` calls with
   `AXIS2_ENV_CHECK_VOID(env)`.

 Sometimes env variable is corrupted. We need to check if it's
 correct.