Ask for all warnings when compiling in a checkout dir
Fix spelling of cloning
Remove NO_INIT vars

According to the XS docs, this is for variables that will be used for output,
not unused input vars.
Use signed char instead of unsigned for BER-related code

This should be fine since BER is all about base 128. Regardless, we're putting
data into or getting it from an SVPV, which uses a standard "char *" to store
the data, so the unsigned-ness is lost.
Remove a few unsigned variables