+ improve check in misc/Makefile.in for empty $PKG_CONFIG_LIBDIR
+ modify wnoutrefresh to call pnoutrefresh if its parameter is a pad,
rather than treating it as an error, and modify new_panel to permit
its window-parameter to be a pad (report by Giorgos Xou).
+ fix a memory-leak in del_curterm (prompted by discussion with Bram
Moolenaar, cf: 20210821).