defrag: pass u64 to ParseU64

Fixes: defrag-config.c:97: warning: passing argument 2 \
       of 'ParseSizeStringU64' from incompatible pointer type
log-http: fix compiler warning

log-httplog.c:180: warning: 'cvalue' may be used uninitialized in \
this function
dns: fix passing NULL to memcpy

app-layer-dns-common.c:401:5: warning: Null pointer passed as \
                              an argument to a 'nonnull' parameter
    memcpy(ptr, fqdn, fqdn_len);
http: clear header pointer on realloc failure

Fixes:

detect-engine-hhd.c:188:5: warning: Use of memory after it is freed
    return headers_buffer;
dns: suppress harmless cppcheck warning

[src/app-layer-dns-common.c:273]: (warning) Assignment of function \
                        parameter has no effect outside the function.
dns: suppress minor scan-build warnings

These were only used if debug is enabled.

app-layer-dns-tcp.c:407:13: warning: Value stored to 'length' is never read
            length = *data;
app-layer-dns-udp.c:236:13: warning: Value stored to 'length' is never read
            length = *data;
stream: suppress minor scan-build warnings

stream-tcp-reassemble.c:2569:17: warning: Value stored to 'seg' is never read
                seg = seg->next;
                ^     ~~~~~~~~~
stream-tcp-reassemble.c:2587:17: warning: Value stored to 'seg' is never read
                seg = seg->next;
detect-ssl: suppress harmless scan-build warning

detect-ssl-version.c:271:17: warning: Value stored to 'neg' is never read
                neg = 0;
DER decoding: fix potential memory leak

This would only happen in memory failure conditions.

util-decode-der.c:634:27: warning: Potential leak of memory pointed to by 'child'
    return (Asn1Generic *)node;
debug: fix realloc error checking on flowbit print

detect.c:1074:17: warning: Potential leak of memory pointed to by \
                                field 'debuglog_flowbits_names'
                return;

Bug #1062.