QUIC: unroll and inline ngx_quic_varint_len()/ngx_quic_build_int(). According to profiling, those two are among most frequently called, so inlining is generally useful, and unrolling should help with it. Further, this fixes undefined behaviour seen with invalid values. Inspired by Yu Liu.

# Copyright (C) Igor Sysoev
# Copyright (C) Nginx, Inc.


cat << END >> $NGX_AUTO_CONFIG_H

#ifndef $have
#define $have  $value
#endif

END