Add strndup() compat function for OSX

The comment in connect_https_socket() suggests that I didn't use strndup()
there because Solaris lacks it. I blithely went ahead and used it in the
NTLM code though, and Solaris 11 *does* seem to have it. (My Solaris 10 VM
no longer boots, and I can't bring myself to care.)

But OSX (10.6.8 Snow Leopard) also seems to lack strndup(). So add a
compat implementation of it rather than just trying to remember not to
use it.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

compat.c

@@ -165,6 +165,23 @@ char *openconnect__strcasestr(const char *haystack, const char *needle)
 }
 #endif
 
+#ifndef HAVE_STRNDUP
+char *openconnect__strndup(const char *s, size_t n)
+{
+	char *r;
+
+	if (n > strlen(s))
+		n = strlen(s);
+
+	r = malloc(n + 1);
+	if (r) {
+		memcpy(r, s, n);
+		r[n] = 0;
+	}
+	return r;
+}
+#endif
+
 #ifndef HAVE_SETENV
 int openconnect__setenv(const char *name, const char *value, int overwrite)
 {

configure.ac

@@ -105,6 +105,7 @@ AC_CHECK_FUNC(fdevname_r, [AC_DEFINE(HAVE_FDEVNAME_R, 1, [Have fdevname_r() func
 AC_CHECK_FUNC(getline, [AC_DEFINE(HAVE_GETLINE, 1, [Have getline() function])],
     [symver_getline="openconnect__getline;"])
 AC_CHECK_FUNC(strcasestr, [AC_DEFINE(HAVE_STRCASESTR, 1, [Have strcasestr() function])], [])
+AC_CHECK_FUNC(strndup, [AC_DEFINE(HAVE_STRNDUP, 1, [Have strndup() function])], [])
 AC_CHECK_FUNC(asprintf, [AC_DEFINE(HAVE_ASPRINTF, 1, [Have asprintf() function])], [])
 if test -n "$symver_asprintf"; then
   AC_MSG_CHECKING([for va_copy])

openconnect-internal.h

@@ -444,6 +444,11 @@ ssize_t openconnect__getline(char **lineptr, size_t *n, FILE *stream);
 #define strcasestr openconnect__strcasestr
 char *openconnect__strcasestr(const char *haystack, const char *needle);
 #endif
+#ifndef HAVE_STRNDUP
+#undef strndup
+#define strndup openconnect__strndup
+char *openconnect__strndup(const char *s, size_t n);
+#endif
 #ifndef HAVE_SETENV
 #define setenv openconnect__setenv
 int openconnect__setenv(const char *name, const char *value, int overwrite);