2. tsem_xxx for mac

2. for the sake of SIGALRM used in the base code, add taos_block_sigalrm and so forth
3. TODO: getaddrinfo would block a few unnecessary seconds when host ~ *.local
         better give warning/suggestion message to user, or just bypass getaddrinfo
         and fail the function

[TD-2671]<fix>:support create/drop/alter stable

[TD-2719]trace subquery states

[TD-2697]<fix>: fix buffer overflow

[TD-2759]<enhance>: remove 1s additional check peer conn timer interval

Fix some small pieces of documents.

[TD-2639] <docs>: fix minor typo.

[<fix> set child table rang error]

[TD-2777] <fix>: fix potential risk to execute rm -rf /

[TD-2451]<test>: add test case

[TD-2639] <docs>: fix a code format.

2. initial port of taosd for MacOSX

[TD-2639] <docs>: fix minor typo.

Feature/query