VS: Fix /MANIFESTUAC: link flag mapping for v142

Apply the change from commit 454b47ba0b (VS: Fix MANIFESTUAC link flag
map to .vcxproj elements, 2018-11-21) to the v142 flag table.

Add special parsing of the flags given in `/MANIFESTUAC:"..."` in order
to map them correctly to `.vcxproj` elements.

Keep the old incorrect flag table entries for `uiAccess` and `level`
flags for compatibility even though they do not really exist.

Templates/MSBuild/FlagTables/v142_Link.json

@@ -644,22 +644,15 @@
     "value": "true",
     "flags": []
   },
-  {
-    "name": "EnableUAC",
-    "switch": "MANIFESTUAC:NO",
-    "comment": "Enable User Account Control (UAC)",
-    "value": "false",
-    "flags": []
-  },
   {
     "name": "EnableUAC",
     "switch": "MANIFESTUAC:",
-    "comment": "Enable User Account Control (UAC)",
+    "comment": "",
-    "value": "true",
+    "value": "",
     "flags": [
       "UserValue",
-      "UserIgnored",
+      "UserRequired",
-      "Continue"
+      "SpaceAppendable"
     ]
   },
   {
@@ -672,16 +665,6 @@
       "UserRequired"
     ]
   },
-  {
-    "name": "UACUIAccess",
-    "switch": "MANIFESTUAC:",
-    "comment": "UAC Bypass UI Protection",
-    "value": "true",
-    "flags": [
-      "UserValue",
-      "UserRequired"
-    ]
-  },
   {
     "name": "UACUIAccess",
     "switch": "uiAccess='false'",