Include less of the generated modular QAPI headers

In my "build everything" tree, a change to the types in
qapi-schema.json triggers a recompile of about 4800 out of 5100
objects.

The previous commit split up qmp-commands.h, qmp-event.h, qmp-visit.h,
qapi-types.h.  Each of these headers still includes all its shards.
Reduce compile time by including just the shards we actually need.

To illustrate the benefits: adding a type to qapi/migration.json now
recompiles some 2300 instead of 4800 objects.  The next commit will
improve it further.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20180211093607.27351-24-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
[eblake: rebase to master]
Signed-off-by: Eric Blake <eblake@redhat.com>

include/qapi/clone-visitor.h

@@ -12,7 +12,6 @@
 #define QAPI_CLONE_VISITOR_H
 
 #include "qapi/visitor.h"
-#include "qapi-visit.h"
 
 /*
  * The clone visitor is for direct use only by the QAPI_CLONE() macro;

include/qapi/error.h

@@ -115,7 +115,7 @@
 #ifndef ERROR_H
 #define ERROR_H
 
-#include "qapi-types.h"
+#include "qapi/qapi-types-common.h"
 
 /*
  * Overall category of an error.

include/qapi/qmp/qobject.h

@@ -32,7 +32,7 @@
 #ifndef QOBJECT_H
 #define QOBJECT_H
 
-#include "qapi-types.h"
+#include "qapi-builtin-types.h"
 
 struct QObject {
     QType type;

include/qapi/visitor.h

@@ -15,7 +15,7 @@
 #ifndef QAPI_VISITOR_H
 #define QAPI_VISITOR_H
 
-#include "qapi-types.h"
+#include "qapi-builtin-types.h"
 
 /*
  * The QAPI schema defines both a set of C data types, and a QMP wire