Remove shmemx.h from shmem.h. Add shmem.h to shmemx.h

Fixes #2483
Signed-off-by: Joshua Ladd <joshual@mellanox.com>

oshmem/include/shmem.h.in

@@ -48,7 +48,6 @@
 #endif
 
 #include <shmem-compat.h>
-#include <shmemx.h>
 
 #if defined(c_plusplus) || defined(__cplusplus)
 extern "C" {

oshmem/include/shmemx.h

@@ -12,6 +12,8 @@
 #ifndef OSHMEM_SHMEMX_H
 #define OSHMEM_SHMEMX_H
 
+#include <shmem.h>
+
 #if defined(c_plusplus) || defined(__cplusplus)
 extern "C" {
 #endif