Add test to import function and call it

lib/runtime-c-api/tests/test-import-function.c

@@ -0,0 +1,46 @@
+#include <stdio.h>
+#include "../wasmer.h"
+#include <assert.h>
+#include <stdint.h>
+
+static print_str_called = false;
+
+void print_str(int32_t ptr, int32_t len, wasmer_instance_context_t *ctx) {
+    printf("In print_str\n");
+    print_str_called = true;
+}
+
+int main()
+{
+    wasmer_import_object_t *import_object = wasmer_import_object_new();
+    wasmer_imports_set_import_func(import_object, "env", "print_str", print_str);
+
+    // Read the wasm file bytes
+    FILE *file = fopen("wasm_sample_app.wasm", "r");
+    fseek(file, 0, SEEK_END);
+    long len = ftell(file);
+    uint8_t *bytes = malloc(len);
+    fseek(file, 0, SEEK_SET);
+    fread(bytes, 1, len, file);
+    fclose(file);
+
+    wasmer_instance_t *instance = NULL;
+    wasmer_compile_result_t compile_result = wasmer_instantiate(&instance, bytes, len, import_object);
+    printf("Compile result:  %d\n", compile_result);
+    assert(compile_result == WASMER_COMPILE_OK);
+
+    wasmer_value_t params[] = {};
+    wasmer_value_t results[] = {};
+    wasmer_call_result_t call_result = wasmer_instance_call(instance, "hello_wasm", params, 0, results, 0);
+    printf("Call result:  %d\n", call_result);
+    assert(call_result == WASMER_CALL_OK);
+
+    assert(print_str_called);
+
+    // TODO review import object ownership, instantiate moves it
+    printf("Destroy instance\n");
+    //wasmer_instance_destroy(instance); // TODO error here
+    printf("Destroy import object\n");
+    //wasmer_import_object_destroy(import_object); // TODO error here
+    return 0;
+}