ncurses 6.2 - patch 20200531

ncurses 6.2 - patch 20200531

+ correct configure version-check/warnng for g++ to allow for 10.x
+ re-enable "bel" in konsole-base (report by Nia Huang)
+ add linux-s entry (patch by Alexandre Montaron).
+ drop long-obsolete convert_configure.pl
+ add test/test_parm.c, for checking tparm changes.
+ improve parameter-checking for tparm, adding function _nc_tiparm() to
  handle the most-used case, which accepts only numeric parameters
  (report/testcase by "puppet-meteor").
+ use a more conservative estimate of the buffer-size in lib_tparm.c's
  save_text() and save_number(), in case the sprintf() function
  passes-through unexpected characters from a format specifier
  (report/testcase by "puppet-meteor").
+ add a check for end-of-string in cvtchar to handle a malformed
  string in infotocap (report/testcase by "puppet-meteor").