Support: style/documentation cleanup for format

This is purely a documentation/whitespace cleanup for the format support
functions.

The current style does not duplicate the function/class names in the
documentation; conform to this style.

Additionally, there was a large amount of duplication of comments that added no
real value.  Use block comments for the related sets of functions which are used
for type deduction and parameter container classes.

No functional change.

llvm-svn: 210190