Fixed compiling errors.

makefile

@@ -3,13 +3,10 @@
 all: dataserver simpleclient
 
 reqchannel.o: reqchannel.h reqchannel.cpp
-	#g++-4.7 -c -g reqchannel.cpp
 	g++ -std=c++11 -c -g reqchannel.cpp
     
 dataserver: dataserver.cpp reqchannel.o 
-	#g++-4.7 -g -o 
 	g++ -std=c++11 -g -o dataserver dataserver.cpp reqchannel.o -lpthread
 
 simpleclient: simpleclient.cpp reqchannel.o
-	#g++-4.7 -g -o simpleclient simpleclient.cpp reqchannel.o
 	g++ -std=c++11 -g -o simpleclient simpleclient.cpp reqchannel.o

semaphore.h

@@ -22,7 +22,7 @@
 /*--------------------------------------------------------------------------*/
 
 #include <pthread.h>
-#include <mutex>
+//#include <mutex>
 
 /*--------------------------------------------------------------------------*/
 /* DATA STRUCTURES */ 
@@ -60,9 +60,16 @@ public:
   /* -- SEMAPHORE OPERATIONS */
 
   int P(){
-    Lock();
+    //This is to lock the Semaphore.
+    pthread_mutex_lock( &m );
     
+    //Wait until condition, basically wait until signaled.
+    pthread_cond_wait( &c, &m );
 
+    //Some code here.
+
+    //Unlock the Semaphore.
+    pthread_mutex_unlock( &m );
   }  
       //;
   int V();