Remove some unecessary casts.

These casts were necessary for really old compilers that didn't
keep track of which level of indirection the "constness" applied
to.  For modern compilers, they should be unecessary.

Change-Id: Ia23cebae43fd6f1705016a11f2df4801e9830d24
Merge topic 'wrap-const-cast' into master

8c45343b Remove some unecessary casts.