fixing clang compilation problems

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/util/cooperate.cpp

@@ -16,10 +16,10 @@ Author:
 Notes:
 
 --*/
-#include"z3_omp.h"
 #include"cooperate.h"
 #include"trace.h"
 #include"debug.h"
+#include"z3_omp.h"
 
 struct cooperation_lock {
     omp_nest_lock_t  m_lock;

src/util/memory_manager.cpp

@@ -4,6 +4,7 @@
 #include"trace.h"
 #include"memory_manager.h"
 #include"error_codes.h"
+#include"z3_omp.h"
 // The following two function are automatically generated by the mk_make.py script.
 // The script collects ADD_INITIALIZER and ADD_FINALIZER commands in the .h files.
 // For example, rational.h contains

src/util/scoped_timer.cpp

@@ -58,6 +58,7 @@ Revision History:
 #endif
 #include"util.h"
 #include<limits.h>
+#include"z3_omp.h"
 
 struct scoped_timer::imp {
     event_handler *  m_eh;

src/util/timeout.cpp

@@ -19,6 +19,7 @@ Revision History:
 
 --*/
 #include<iostream>
+#include"z3_omp.h"
 #include"util.h"
 #include"timeout.h"
 #include"error_codes.h"