Add get_jni_java_vm function (#710)

Author: bl1nch

jnius/jnius.pyx

@@ -88,7 +88,7 @@ Python::
 __all__ = ('JavaObject', 'JavaClass', 'JavaMethod', 'JavaField',
            'JavaStaticMethod', 'JavaStaticField', 'JavaMultipleMethod',
            'MetaJavaBase', 'MetaJavaClass', 'JavaException', 'cast',
-           'find_javaclass', 'PythonJavaClass', 'java_method', 'detach')
+           'find_javaclass', 'PythonJavaClass', 'java_method', 'detach', 'get_jni_java_vm')
 
 from libc.stdlib cimport malloc, free
 from functools import partial

jnius/jnius_env.pxi

@@ -1,3 +1,5 @@
+from libc.stdint cimport intptr_t
+
 
 cdef JNIEnv *default_env = NULL
 
@@ -23,3 +25,5 @@ cdef JNIEnv *get_jnienv() except NULL:
 def detach():
     jvm[0].DetachCurrentThread(jvm)
 
+def get_jni_java_vm():
+    return <intptr_t>default_env, <intptr_t>jvm