Implement cdata typemaps for C

Just use the struct directly in the C wrappers.

Examples/test-suite/c/Makefile.in

@@ -33,7 +33,6 @@ FAILING_C_TESTS := \
     function_typedef \
     lextype \
     li_carrays \
-    li_cdata \
     li_cpointer \
     nested \
     nested_extend_c \

Lib/cdata.i

@@ -21,6 +21,28 @@ typedef struct SWIGCDATA {
 }
 %typemap(in) (const void *indata, int inlen) = (char *STRING, int LENGTH);
 
+#elif SWIGC
+
+%insert("cheader") {
+typedef struct SWIGCDATA {
+    char *data;
+    int   len;
+} SWIGCDATA;
+}
+
+%typemap(ctype) SWIGCDATA "SWIGCDATA"
+%typemap(cppouttype) SWIGCDATA "SWIGCDATA"
+
+%typemap(out) SWIGCDATA {
+    $result = $1;
+}
+
+%typemap(ctype) (const void *indata, int inlen) "const SWIGCDATA*"
+%typemap(in) (const void *indata, int inlen) {
+    $1 = $input->data;
+    $2 = $input->len;
+}
+
 #elif SWIGCHICKEN
 
 %typemap(out) SWIGCDATA {