Fix memory leak in C examples.

examples/HelloArgonInC.c

@@ -26,11 +26,13 @@ void simulateArgon()
     OpenMM_Platform*       platform;
     OpenMM_NonbondedForce* nonbond; 
     OpenMM_Vec3Array*      initPosInNm;
+    OpenMM_StringArray*    pluginList;
     int                    a, frameNum;
 
     /* Load any shared libraries containing GPU implementations. */
-    OpenMM_Platform_loadPluginsFromDirectory(
+    pluginList = OpenMM_Platform_loadPluginsFromDirectory(
         OpenMM_Platform_getDefaultPluginsDirectory());
+    OpenMM_StringArray_destroy(pluginList);
 
     /* Create a system with nonbonded forces. System takes ownership
        of Force; don't destroy it yourself. */

examples/HelloSodiumChlorideInC.c

@@ -197,14 +197,16 @@ myInitializeOpenMM( const MyAtomInfo    atoms[],
     MyOpenMMData* omm = (MyOpenMMData*)malloc(sizeof(struct MyOpenMMData_s));
     /* These are temporary OpenMM objects used and discarded here. */
     OpenMM_Vec3Array*       initialPosInNm;
+    OpenMM_StringArray*     pluginList;
     OpenMM_NonbondedForce*  nonbond;
     OpenMM_GBSAOBCForce*    gbsa;
     OpenMM_Platform*        platform;
     int n;
 
     /* Load all available OpenMM plugins from their default location. */
-    OpenMM_Platform_loadPluginsFromDirectory
+    pluginList = OpenMM_Platform_loadPluginsFromDirectory
        (OpenMM_Platform_getDefaultPluginsDirectory());
+    OpenMM_StringArray_destroy(pluginList);
 
     /* Create a System and Force objects within the System. Retain a reference
      * to each force object so we can fill in the forces. Note: the OpenMM