MFC r299710,r299711,r299763,r299783,r299811:

r299710:

Staticize global variables only used in bsnmpimport.c to fix
-Wmissing-variable-declarations warnings

r299711:

Fold two malloc + memset(.., 0, ..) calls into equivalent calloc calls

r299763:

Mute -Wstrlcpy-strlcat-size warning by using nitems with the size of the buffer

This is a no-op as the malloc above set the size of the buffer to the size used
below, but this keeps things consistent in case the malloc call changes somehow.

r299783:

Convert tok from enum tok to int32_t in function calls

get_token(..) returns int32_t, not enum tok, and in many cases tests for items
not in enum tok (e.g. '('). Make the typing consistent with get_token, which
includes a domino effect of changing enum tok to int32_t.

r299811:

Use strdup instead of malloc + strlcpy

Fix error messages on failure for calloc/strdup