ProcessManager+top: Rename "linear" size to "virtual" size.

I originally called it "linear" because that's how the Intel manual names
virtual addresses in many cases. I'm ready to accept that most people know
this as "virtual" so let's just call it that.

Applications/ProcessManager/ProcessModel.h

@@ -20,7 +20,7 @@ public:
         Priority,
         User,
         PID,
-        Linear,
+        Virtual,
         Physical,
         Syscalls,
         __Count
@@ -48,8 +48,8 @@ private:
         String state;
         String user;
         String priority;
-        size_t linear;
-        size_t physical;
+        size_t virtual_size;
+        size_t physical_size;
         unsigned syscalls;
         float cpu_percent;
     };