Check component and derive names for canDerive and get (AMReX-Cod…

…es#3109)

`canDerive` and `get` in the `DeriveList` class only check the derive
name but not the variable component names. This code adds a check on the
variable names. @esclapez did this internally for PeleLMeX and we need
it for PeleC as well so I thought this should just belong in AMReX.

Src/Amr/AMReX_Derive.cpp

@@ -430,6 +430,12 @@ DeriveList::canDerive (const std::string& name) const
          li != End;
          ++li)
     {
+        // Can be either a component name ...
+        for (int i = 0; i < li->numDerive(); i++) {
+           if (li->variableName(i) == name)
+               return true;
+        }
+        // ... or a derive name
         if (li->derive_name == name)
             return true;
     }
@@ -443,6 +449,12 @@ DeriveList::get (const std::string& name) const
          li != End;
          ++li)
     {
+        // Can be either a component name ...
+        for (int i = 0; i < li->numDerive(); i++) {
+           if (li->variableName(i) == name)
+               return &(*li);
+        }
+        // ... or a derive name
         if (li->derive_name == name)
             return &(*li);
     }