DOC: update RELEASE.rst

PTF

Author: y-p

RELEASE.rst

@@ -48,7 +48,8 @@ pandas 0.12.0
   - Fixed an esoteric excel reading bug, xlrd>= 0.9.0 now required for excel
     support. Should provide python3 support (for reading) which has been
     lacking. (GH3164_)
-  - Fix to_csv issue when having a large number of rows and ``NaT`` in some 
+  - Addressed handling of dupe columns in df.to_csv new and old (GH3454_, GH3457_)
+  - Fix to_csv issue when having a large number of rows and ``NaT`` in some
     columns (GH3437_)
   - ``.loc`` was not raising when passed an integer list (GH3449_)
   - Unordered time series selection was misbehaving when using label slicing (GH3448_)
@@ -57,6 +58,8 @@ pandas 0.12.0
 .. _GH3164: https://github.com/pydata/pandas/issues/3164
 .. _GH3251: https://github.com/pydata/pandas/issues/3251
 .. _GH3379: https://github.com/pydata/pandas/issues/3379
+.. _GH3454: https://github.com/pydata/pandas/issues/3454
+.. _GH3457: https://github.com/pydata/pandas/issues/3457
 .. _GH3038: https://github.com/pydata/pandas/issues/3038
 .. _GH3437: https://github.com/pydata/pandas/issues/3437
 .. _GH3455: https://github.com/pydata/pandas/issues/3455