Fix the modules/mysqlx/AMBuilder not building on Visual Studio 2015 (#397)

* Fix the modules/mysqlx/AMBuilder not building on Visual Studio 2015

Applied the same fix as in:

Fix building of MySQL DBI extension on VS 2015+ by psychonic:
94383d995d

* Removed the msvc15hack.c from the sources when not necessary.

modules/mysqlx/AMBuilder

@@ -15,6 +15,8 @@ if AMXX.mysql_path:
     'HAVE_STDINT_H',
   ]
 
+  binary.sources = []
+
   if builder.target_platform is 'linux' or builder.target_platform is 'mac':
     binary.compiler.defines += ['stricmp=strcasecmp']
     binary.compiler.linkflags += [
@@ -27,10 +29,15 @@ if AMXX.mysql_path:
       os.path.join(AMXX.mysql_path, 'lib', 'opt', 'mysqlclient.lib'),
       'ws2_32.lib'
     ]
+    if binary.compiler.vendor == 'msvc' and binary.compiler.version >= 1900:
+      binary.compiler.linkflags += ['legacy_stdio_definitions.lib', 'legacy_stdio_wide_specifiers.lib']
+      binary.sources += [
+        'msvc15hack.c'
+      ]
 
   binary.compiler.linkflags += [AMXX.zlib.binary]
-    
-  binary.sources = [
+
+  binary.sources += [
     'basic_sql.cpp',
     'handles.cpp',
     'module.cpp',
@@ -47,7 +54,7 @@ if AMXX.mysql_path:
 
   if builder.target_platform == 'windows':
     binary.sources += ['version.rc']
-    
+
   if builder.target_platform == 'windows':
     binary.sources += [
       'thread/WinThreads.cpp',