libu2fmisc: possible data truncation due to long <> int implicit conversion

[iam-TJ]

Building the binary helper for v0.0.13 on x86_64 host:

/home/all/SourceCode/yubikey/u2f4moz/c_src/libu2f-host/u2fmisc.c: In function ‘send_apdu’:
/home/all/SourceCode/yubikey/u2f4moz/c_src/libu2f-host/u2fmisc.c:328:18: warning: format ‘%c’ expects argument of type ‘int’, but argument 8 has type ‘size_t {aka long unsigned int}’ [-Wformat=]
sprintf (data, "%c%c%c%c%c%c%c", 0, cmd, p1, 0, 0, (dlen >> 8) & 0xff,
^
/home/all/SourceCode/yubikey/u2f4moz/c_src/libu2f-host/u2fmisc.c:328:18: warning: format ‘%c’ expects argument of type ‘int’, but argument 9 has type ‘size_t {aka long unsigned int}’ [-Wformat=]