* Moves -Wunused-dummy-arguments to the developer warnings since this
generates a lot of spurious, unfixable noise due to things like
callback wrappers
* Changes the return cast in h5fget_fileno_c, fixes a comment, and comment
on potential badness
* Initializes a variable in tH5L_F03.F90 to quiet a 'maybe
uninitialized' warning
