ipa-kdb: add missing prototypes
    
    On Fedora 33 GCC defaults to -Wmissing-prototypes and emits warnings
    about function prototypes missing. If -Werror is specified, this breaks
    compilation.
    
    We also default to -Werror=implicit-function-declaration
    
    Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Robbie Harwood <rharwood@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>