Use an extension to denote vendorized code.

Vendorized code is copied from another project when a library is not available and a git subproject won't work. Currently all the vendorized code is copied from PostgreSQL but it makes sense to have a more general mechanism for indicating vendorized code.

The .vendor extension will be used to denote vendorized code in the same way that .auto is used to denote auto-generated code.

test/lib/pgBackRestTest/Common/CodeCountTest.pm

@@ -98,6 +98,12 @@ sub codeCountScan
             $strClass .= '/auto';
         }
 
+        # Append vendor if a vendorized file
+        if ($strFile =~ '\.vendor\..$')
+        {
+            $strClass .= '/vendor';
+        }
+
         # Force unrecognized file types
         my $strForceLang = undef;
         my $strType = undef;