Fix JNI compiler for synchronized methods.

Calls to the monitor enter/exit routines were passing the JNI env with
the iterator in the wrong position. Reset the iterator to make sure it
is in the correct position for the monitor enter/exit call.

Also fix clobbering of arguments in registers when calling monitor enter
for synchronized methods on ARM.

Also some tidying of code/comments.

Change-Id: I5bf1dd7e65d925e768411cb5865919ee5f54edbf
diff --git a/src/globals.h b/src/globals.h
index b7096e6..777cfd6 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -32,6 +32,8 @@
 const int kBitsPerWord = kWordSize * kBitsPerByte;
 const int kBitsPerInt = kIntSize * kBitsPerByte;
 
+// Required stack alignment
+const int kStackAlignment = 16;
 
 // System page size.  Normally you're expected to get this from
 // sysconf(_SC_PAGESIZE) or some system-specific define (usually