C++: Add upgrade and downgrade scripts

cpp/downgrades/59cb96ca699929b63941e81905f9b8de7eed59a6/preprocdirects.ql

@@ -0,0 +1,21 @@
+class PreprocessorDirective extends @preprocdirect {
+  string toString() { none() }
+}
+
+class Location extends @location_default {
+  string toString() { none() }
+}
+
+bindingset[kind]
+int getKind(int kind) {
+  if kind = 14
+  then result = 6 // Represent MSFT #import as #include
+  else
+    if kind = 15 or kind = 6
+    then result = 3 // Represent #elifdef and #elifndef as #elif
+    else result = kind
+}
+
+from PreprocessorDirective ppd, int kind, Location l
+where preprocdirects(ppd, kind, l)
+select ppd, getKind(kind), l

cpp/downgrades/59cb96ca699929b63941e81905f9b8de7eed59a6/upgrade.properties

@@ -0,0 +1,3 @@
+description: Support #elifdef, #elifndef and #import
+compatibility: full
+preprocdirects.rel: run preprocdirects.qlo

cpp/ql/lib/upgrades/1aa71a4a687fc93f807d4dfeeef70feceeced242/upgrade.properties

@@ -0,0 +1,2 @@
+description: Support #elifdef, #elifndef and #import
+compatibility: partial