Don't introduce Catch::Matchers namespace in macro

- this could be a breaking change - fixed up self-test code to compensate

projects/SelfTest/MiscTests.cpp

@@ -208,6 +208,7 @@ inline const char* testStringForMatching()
 {
     return "this string contains 'abc' as a substring";
 }
+using namespace Catch::Matchers;
 
 TEST_CASE("String matchers", "[matchers]" )
 {

projects/SelfTest/TagAliasTests.cpp

@@ -11,6 +11,8 @@
 
 TEST_CASE( "Tag alias can be registered against tag patterns", "" ) {
 
+    using namespace Catch::Matchers;
+
     Catch::TagAliasRegistry registry;
 
     registry.add( "[@zzz]", "[one][two]", Catch::SourceLineInfo( "file", 2 ) );

projects/SelfTest/TestMain.cpp

@@ -44,6 +44,8 @@ inline Catch::TestCase fakeTestCase( const char* name, const char* desc = "" ){
 
 TEST_CASE( "Process can be configured on command line", "[config][command-line]" ) {
 
+    using namespace Catch::Matchers;
+
     Catch::ConfigData config;
 
     SECTION( "default - no arguments", "" ) {