Minor fixes

[nosnilmot]

Fixes for a compile warning:

src/handler.c: In function 'handler_system_delete_all':
src/handler.c:706:25: warning: 'key2' may be used uninitialized in this function [-Wmaybe-uninitialized]
                 hash_add(conn->id_handlers, key2, head);

and a compile failure when not compiling in C99 mode (default for gcc 4.8.5 on CentOS/RHEL 7):

examples/perf.c: In function ‘perf_rand’:
examples/perf.c:42:5: error: ‘for’ loop initial declarations are only allowed in C99 mode
     for (size_t sz = 2; sz <= alloc_sz; sz <<= 1) {