check for stpcpy

needed for popt on macos

Author: tridge

configure.ac

@@ -870,7 +870,7 @@ AC_CHECK_FUNCS(waitpid wait4 getcwd chown chmod lchmod mknod mkfifo \
     fchmod fstat ftruncate strchr readlink link utime utimes lutimes strftime \
     chflags getattrlist mktime innetgr linkat \
     memmove lchown vsnprintf snprintf vasprintf asprintf setsid strpbrk \
-    strlcat strlcpy strtol mallinfo mallinfo2 getgroups setgroups geteuid getegid \
+    strlcat strlcpy stpcpy strtol mallinfo mallinfo2 getgroups setgroups geteuid getegid \
     setlocale setmode open64 lseek64 mkstemp64 mtrace va_copy __va_copy \
     seteuid strerror putenv iconv_open locale_charset nl_langinfo getxattr \
     extattr_get_link sigaction sigprocmask setattrlist getgrouplist \