[PATCH] Small refactoring of inval.c and inval.h

Hi,

The proposed patch is a small refactoring of inval.{c,h}:

"""
    The "public functions" separator comment doesn't reflect reality anymore.
    We could rearrange the order of the functions. However, this would
complicate
    back-porting of the patches, thus removing the comment instead.

    InvalidateSystemCachesExtended() is an internal function of inval.c. Make it
    static.
"""

-- 
Best regards,
Aleksander Alekseev