Make c_api compatible with configure'd makefile (#477)

c_api/example_c.c

@@ -27,7 +27,7 @@
         }                                                  \
     }
 
-inline double drand() {
+double drand() {
     return (double)rand() / (double)RAND_MAX;
 }
 
@@ -94,4 +94,4 @@ int main() {
     printf("Done.\n");
 
     return 0;
-}
+}