Add a new reporter customization point: reporting all assertions

By opting the JUnit and XML reporters into it, we no longer run
into problem where they underreport the results without `-s` flag.

Related to #1264, #1267, #1310

include/reporters/catch_reporter_junit.cpp

@@ -62,6 +62,7 @@ namespace Catch {
             xml( _config.stream() )
         {
             m_reporterPrefs.shouldRedirectStdOut = true;
+            m_reporterPrefs.shouldReportAllAssertions = true;
         }
 
     JunitReporter::~JunitReporter() {}