[RELEASE] c-ares 1.21.0

[Daniel Stenberg]

Hi friends.

We are happy to once again ship another c-ares release. Get it as always from 
https://c-ares.org/

c-ares version 1.21.0

This is a bugfix and cleanup release with some significant internal changes.

Changes:
  o Provide better man page cross-links. [1]
  o Introduce ares_status_t as an enum rather than using #define list and
    integer data type for internal functions. [2]
  o Introduce ares_bool_t datatype rather than using an integer with 0/1 so
    it is clear based on the function prototype what it returns. [5]
  o Increase compiler warning levels by default. [6]
  o Use size_t and other more proper datatypes internally (rather than int). [7]
  o Many developers have used different code styles over the years, standardize
    on one and use clang-format to enforce the style. [8]
  o CMake can now control symbol visibility [9]
  o Replace multiple DNS hand-made parsers with new memory-safe DNS message
    parser. [10]

Bug Fixes:
  o Tools: STAYOPEN flag could make tools not terminate. [3]
  o Socket callbacks were passed SOCK_STREAM instead of SOCK_DGRAM on udp. [4]

Thanks go to these friendly people for their efforts and contributions:
   Brad House (@bradh352)
   Daniel Stenberg (@bagder)
   Gregor Jasny (@gjasny)
(3 contributors)

References to bug reports and discussions on issues:
  [1] = https://github.com/c-ares/c-ares/pull/565
  [2] = https://github.com/c-ares/c-ares/pull/567
  [3] = https://github.com/c-ares/c-ares/pull/569
  [4] = https://github.com/c-ares/c-ares/commit/a070d78
  [5] = https://github.com/c-ares/c-ares/pull/570
  [6] = https://github.com/c-ares/c-ares/pull/568
  [7] = https://github.com/c-ares/c-ares/pull/573
  [8] = https://github.com/c-ares/c-ares/pull/579
  [9] = https://github.com/c-ares/c-ares/pull/574
  [10] = https://github.com/c-ares/c-ares/pull/581

-- 

  / daniel.haxx.se