Sync for upcoming vc++ 15.6 version raise

Author: weltling

win32/build/confutils.js

@@ -72,6 +72,7 @@ VC_VERSIONS[1900] = 'MSVC14 (Visual C++ 2015)';
 VC_VERSIONS[1910] = 'MSVC15 (Visual C++ 2017)';
 VC_VERSIONS[1911] = 'MSVC15 (Visual C++ 2017)';
 VC_VERSIONS[1912] = 'MSVC15 (Visual C++ 2017)';
+VC_VERSIONS[1913] = 'MSVC15 (Visual C++ 2017)';
 
 var VC_VERSIONS_SHORT = new Array();
 VC_VERSIONS_SHORT[1200] = 'VC6';
@@ -86,6 +87,7 @@ VC_VERSIONS_SHORT[1900] = 'VC14';
 VC_VERSIONS_SHORT[1910] = 'VC15';
 VC_VERSIONS_SHORT[1911] = 'VC15';
 VC_VERSIONS_SHORT[1912] = 'VC15';
+VC_VERSIONS_SHORT[1913] = 'VC15';
 
 if (PROGRAM_FILES == null) {
 	PROGRAM_FILES = "C:\\Program Files";