Cleanup and refactor Fortran shared memory usage

also added some missing locking for the ipc(1) value in ft8_decode().

lib/shmem.cpp

@@ -0,0 +1,20 @@
+#include <QSharedMemory>
+#include <QLatin1String>
+
+// Multiple instances: KK1D, 17 Jul 2013
+QSharedMemory shmem;
+
+struct jt9com;
+
+// C wrappers for a QSharedMemory class instance
+extern "C"
+{
+  bool shmem_create (int nsize) {return shmem.create(nsize);}
+  void shmem_setkey (char * const mykey) {shmem.setKey(QLatin1String{mykey});}
+  bool shmem_attach () {return shmem.attach();}
+  int shmem_size () {return static_cast<int> (shmem.size());}
+  struct jt9com * shmem_address () {return reinterpret_cast<struct jt9com *>(shmem.data());}
+  bool shmem_lock () {return shmem.lock();}
+  bool shmem_unlock () {return shmem.unlock();}
+  bool shmem_detach () {return shmem.detach();}
+}