Reduce intermittent test failures in CI by fixing bugs found by asan …

…and tsan (#926)

* Fix intermittent crashes in TestContinuationsWithTask.

The one now marked 7 was creating a task that wrote to a stack variable,
but never joined with that stack variable. This would cause random
crashes whenever that stack position got clobbered.

* Fix several errors found by thread sanitizer.

* Fix more data races :/

* Fix data races in the asio server found by tsan.

* Avoid VS2015 warning C4800.

Release/include/cpprest/astreambuf.h

@@ -13,10 +13,11 @@
 ****/
 #pragma once
 
+#include <math.h>
+#include <atomic>
+#include <cstring>
 #include <ios>
 #include <memory>
-#include <cstring>
-#include <math.h>
 
 #include "pplx/pplxtasks.h"
 #include "cpprest/details/basic_types.h"
@@ -745,7 +746,10 @@ namespace streams
 
         std::exception_ptr m_currentException;
         // The in/out mode for the buffer
-        bool m_stream_can_read, m_stream_can_write, m_stream_read_eof, m_alloced;
+        std::atomic<bool> m_stream_can_read;
+        std::atomic<bool> m_stream_can_write;
+        std::atomic<bool> m_stream_read_eof;
+        std::atomic<bool> m_alloced;
 
 
     private:
@@ -1208,5 +1212,3 @@ namespace streams
     };
 
 }}
-
-

Release/include/pplx/pplxlinux.h

@@ -29,7 +29,8 @@
 #include <boost/thread/mutex.hpp>
 #include <boost/thread/condition_variable.hpp>
 #else
-#include <mutex>   
+#include <mutex>
+#include <atomic>
 #include <condition_variable>
 #endif
 
@@ -80,7 +81,7 @@ namespace platform
         static const unsigned int timeout_infinite = 0xFFFFFFFF;
 
         event_impl()
-            : _signaled(false) 
+            : _signaled(false)
         {
         }
 
@@ -209,7 +210,7 @@ namespace platform
                 _M_cs.lock();
                 _M_owner = id;
                 _M_recursionCount = 1;
-            }            
+            }
         }
 
         void unlock()
@@ -223,12 +224,12 @@ namespace platform
             {
                 _M_owner = -1;
                 _M_cs.unlock();
-            }           
+            }
         }
 
     private:
         cpprest_synchronization::mutex _M_cs;
-        volatile long _M_owner;
+        std::atomic<long> _M_owner;
         long _M_recursionCount;
     };
 
@@ -298,7 +299,7 @@ namespace extensibility
 #else
     typedef details::linux_scheduler default_scheduler_t;
 #endif
-    
+
 namespace details
 {
     /// <summary>