Problem: some call of INET_NTOA() function may lead 
to a crash due to missing its character set initialization.

Fix: explicitly set the character set.


mysql-test/r/func_misc.result:
  Fix for bug#57283: inet_ntoa() crashes
    - test result.
mysql-test/t/func_misc.test:
  Fix for bug#57283: inet_ntoa() crashes
    - test case.
sql/item_strfunc.cc:
  Fix for bug#57283: inet_ntoa() crashes
    - explicitly set buffer's character set.