core: spelling fixes

src/core/model/int64x64.h

@@ -151,7 +151,7 @@ inline bool operator >= (const int64x64_t & lhs, const int64x64_t & rhs)
  * Output streamer for int64x64_t.
  *
  * Values are printed with the following format flags
- * (independent of the the stream flags):
+ * (independent of the stream flags):
  *   - `showpos`
  *   - `left`
  *

src/core/model/object-base.h

@@ -158,7 +158,7 @@ public:
   /**
    * Set a single attribute without raising errors.
    *
-   * If the atttribute could not be set this will return \c false,
+   * If the attribute could not be set this will return \c false,
    * but not raise any errors.
    *
    * \param [in] name The name of the attribute to set.