core: default size for shared memory is 64MB

- decent size at least for 64b architecture where pointer overhead is
  bigger

config.h

@@ -148,7 +148,7 @@
 #endif
 #define PKG_MEM_POOL_SIZE PKG_MEM_SIZE*1024*1024	/*!< used only if PKG_MALLOC is defined*/
 
-#define SHM_MEM_SIZE 32				/*!< used if SH_MEM is defined*/
+#define SHM_MEM_SIZE 64				/*!< used if SH_MEM is defined*/
 
 
 /* dimensioning buckets in q_malloc */