Fix -Wmissing-prototypes and -Wunused-function warnings
Fix -Wmissing-prototypes and -Wunused-function warnings

Remove unused functions (debug, debug_va_list, and vverbose) and
comment out verbose, as it's currently used in drill/work.c in
commented out code

Reported by: clang 3.8.0, gcc 5.3.0
Signed-off-by: Ngie Cooper <94c72ae9cb99b268ef5bac9a1283c7f5ad375547@gmail.com>

NLnetLabs/ldns,NLnetLabs/ldns,NLnetLabs/ldns,NLnetLabs/ldns