Improve C++ compatibility of previous patch.

* src/gpgme.h.in: Move gpgme_sssize_t and gpgme_off_t typedefs into
the extern "C" scope.
--

Frankly, this does not help very much because g++ still does not
interpret gpgme_data_seek_cb_t as compatible with the C++ ssize_t.  I
am sorry for that API change but C and C++ are too different to always
get both of them under one umbrella.  However, the ABI should now be
identical to older gpgme versions.

src/gpgme.h.in

@@ -34,8 +34,6 @@
 /* Include stdio.h for the FILE type definition.  */
 #include <stdio.h>
 #include <time.h>
-@INSERT__TYPEDEFS_FOR_GPGME_H@
-
 #include <gpg-error.h>
 
 #ifdef __cplusplus
@@ -45,6 +43,7 @@ extern "C" {
 #endif
 #endif /* __cplusplus */
 
+@INSERT__TYPEDEFS_FOR_GPGME_H@
 
 
 /* Check for compiler features.  */