Eliminate "control reaches end of non-void function" warnings.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@32225 91177308-0d34-0410-b5e6-96231b3b80d8

lib/System/Unix/Mutex.inc

@@ -31,16 +31,19 @@ Mutex::~Mutex()
 bool 
 Mutex::acquire()
 {
+  return true;
 }
 
 bool 
 Mutex::release()
 {
+  return true;
 }
 
 bool 
 Mutex::tryacquire( void )
 {
+  return true;
 }
 
 }