tbox v1.6.1 released, add stackless coroutine!

• Stackless introduction
• Stackfull introduction
• More coroutine examples

New features

• Support coroutine context switch for mips
• Add __tb_thread_local__ keyword macro
• Add --micro=y|n option to compiling micro library (~64K) for the embed system
• Add tb_addrinfo_addr and tb_addrinfo_name interfaces
• Add stackless coroutine
• Add semaphone and lock for the stackless coroutine

Changes

• Optimize io scheduler for coroutine, cache events for poller
• Add c11 _Static_assert
• Remove some deprecated interfaces for hash and platform