Some typos fixed

src/db/db/built-in-macros/pcell_declaration_helper.lym

@@ -478,7 +478,7 @@ module RBA
       text
     end
     
-    # implementation of display_text
+    # implementation of cell_name
     def cell_name(parameters)
       self._start
       @param_values = parameters

src/db/db/dbPCellVariant.h

@@ -109,12 +109,12 @@ public:
   virtual std::string get_display_name () const;
 
   /**
-   *  @brief Unregisters a cell from it's context.
+   *  @brief Unregisters a cell from its context.
    */
   virtual void unregister ();
 
   /**
-   *  @brief Re-registers a cell inside it's context.
+   *  @brief Re-registers a cell inside its context.
    */
   virtual void reregister ();