lttng-ust: upgrade 2.13.5 -> 2.13.6

Changelog:
===========
* Fix: segmentation fault on filter interpretation in "switch" mode
* Fix: `ip` context is expressed as a base-10 field
* Fix: c99: use __asm__ __volatile__
* Fix: c99: static assert: clang build fails due to multiple typedef
* Fix: Reevaluate LTTNG_UST_TRACEPOINT_DEFINE each time tracepoint.h is included
* Fix: trace events in C++ constructors/destructors
* Fix: trace events in C constructors/destructors
* Fix: use unaligned pointer accesses for lttng_inline_memcpy

Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>