log: fix obscure crashes due to size_t promotion
log: fix obscure crashes due to size_t promotion

It dawns on me now that I should've been hinting or forcing the type at
all of the LOGGER_LOG endpoints to ensure they match the va_arg side on
logger.c. This patch initially swaps size_t's for int's so at least it's
using less complicated promotion rules.

Fixes a crash on centos 7 when logging sets via `watch mutations`

memcached/memcached,memcached/memcached,memcached/memcached,memcached/memcached,memcached/memcached