add option to map specific C type to Rust type

when bindgen (0.59.2) translate this to Rust

typedef void (* C4NULLABLE C4LogCallback)(C4LogDomain, C4LogLevel, const char *fmt, va_list args);
void c4log_writeToCallback(C4LogLevel level, C4LogCallback callback, bool preformatted) C4API;

I got this type for C4LogCallback.

unsafe extern "C" fn(_, C4LogLevel, _, *mut __va_list_tag)

I want replace the last argument *mut __va_list_tag with VaList from va_list crate.

I also I have similar problem when I convert bitmap.h from Android Sdk.
This header include jni.h and so:

int32_t AndroidBitmap_getDataSpace(JNIEnv* env, jobject jbitmap)

uses generated by bindgen Rust type JNIEnv defined in jni.h,
but at the same time I use jni crate where this type defined,
so I want map C type JNIEnv to jni::JNIEnv.

Reproduce the bindgen 0.59.2 output for the C4LogCallback and Android bitmap declarations, including the types from va_list and jni.h. Then trace how bindgen represents generated C types and determine where a user option could map them to va_list::VaList or jni::JNIEnv; done means both examples can use those mapped Rust types.