Bump version to 2.1.

Compared with 2.0, user space interface is changed. User space is
expected to open \\.\AEHD instead of \\.\gvm now. However, in order
not to break existing user space, \\.\gvm is not removed in this
release. It may be removed in later releases.

Author: Taogle2018

aehd_ver.h

@@ -17,7 +17,7 @@
 #define _XSTR(str) _STR(str)
 
 #define AEHD_MAJOR_VERSION 2
-#define AEHD_MINOR_VERSION 0
+#define AEHD_MINOR_VERSION 1
 
 #define AEHD_VERSION ((AEHD_MAJOR_VERSION << 16) | AEHD_MINOR_VERSION)