Make all nss targets build on Win64

nss.gyp

Index: nss.gyp
===================================================================
--- nss.gyp	(revision 174690)
+++ nss.gyp	(working copy)
@@ -1032,7 +1032,7 @@
           'mozilla/security/nss/lib/util',
         ],
       },
-      'msvs_disabled_warnings': [4018, 4101],
+      'msvs_disabled_warnings': [4018, 4101, 4267, ],
       'conditions': [
         ['exclude_nss_root_certs==1', {
           'defines': [
@@ -1123,6 +1123,18 @@
                 'MP_NO_MP_WORD',
               ],
             }],
+            ['target_arch=="x64"', {
+              'defines': [
+                'NSS_USE_64',
+                'NSS_X86_OR_X64',
+                'NSS_X64',
+                'WIN64',
+              ],
+              'sources!': [
+                'mozilla/security/nss/lib/freebl/mpi/mpi_amd64.c',
+                'mozilla/security/nss/lib/freebl/mpi/mpi_x86_asm.c',
+              ],
+            }],
           ],
         }],
         ['clang==1', {