acedb FTBFS against glibc 2.38

../wh/utils.h:34:7: error: conflicting types for ‘strcasestr’; have ‘char *(char *, char *)’
   34 | char *strcasestr (char *str1, char *str2);
      | ^~~~~~~~~~
In file included from ../wh/mystdlib.h:227,
                 from ../wh/regular.h:51,
                 from utils.c:37:
/usr/include/string.h:380:14: note: previous declaration of ‘strcasestr’ with type ‘char *(const char *, const char *)’
  380 | extern char *strcasestr (const char *__haystack, const char *__needle)
      | ^~~~~~~~~~
utils.c:778:7: error: conflicting types for ‘strcasestr’; have ‘char *(char *, char *)’
  778 | char *strcasestr(char *str1, char *str2)
      | ^~~~~~~~~~
/usr/include/string.h:380:14: note: previous declaration of ‘strcasestr’ with type ‘char *(const char *, const char *)’
  380 | extern char *strcasestr (const char *__haystack, const char *__needle)

In earlier glibc versions, strcasestr was only defined when building with _GNU_SOURCE.
Starting with glibc 2.38, it is available by default.