cpstripped(): Replace malloc()s with statics based on MB_LEN_MAX.

cpstripped(): Replace malloc()s with statics based on MB_LEN_MAX.

MB_CUR_MAX from stdlib.h isn't a compile-time constant so can't be used
for the size of a couple of static char arrays so malloc() was used at
run time, with the tiny claims never being freed.  valgrind(1) noticed
and David suggested MB_LEN_MAX from limits.h instead;  that header's
contents are suitable for #if expressions and thus compile-time
constants.