ncurses 6.4 - patch 20230603

+ add configure option --with-strip-program, to override program
  chosen by the install program for stripping executables (prompted
  by discussion with Aapo Rantalainen).
+ fix typo in INSTALL (report/patch by Aapo Rantalainen).
+ improve error-checks for isEILSEQ()
+ increase MB_CUR_MAX to 16, matching glibc's MB_LEN_MAX.
+ corrected mouse mask in test/testcurs.c
+ improve thread lock in lib_trace.c