Alias handling bug in zjson writer

[henridf]

The zjson writer handles aliases to primitive types ok, but not aliases to container types. (The zjson reader likely has a similar issue).

$ cat alias.tzng 
#0:record[host:ip]
0:[127.0.0.2;]
#myrec=record[host:ip]
#1:record[foo:myrec]
1:[[127.0.0.2;]]
19:21 ~/work/brim/zq(zeekstrings-to-zeekio)
$ zq -f zjson alias.tzng 
{"id":23,"type":[{"name":"host","type":"ip"}],"values":["127.0.0.2"]}
malformed zng value

[philrz]

Verified in zq commit a14daef. The original repro now generate output rather than an error.

$ zq -f zjson alias.tzng
{"id":23,"type":[{"name":"host","type":"ip"}],"values":["127.0.0.2"]}
{"id":25,"type":[{"name":"foo","type":"myrec"}],"aliases":[{"name":"myrec","type":"record[host:ip]"}],"values":[["127.0.0.2"]]}

Thanks @henridf!