Import libxo-1.0.2

Import libxo-1.0.2

from 1.0.0:
    Add "continuation" flag, to allow multiple "xo" invocations in a single line of output (#58)
    Add --top-wrap to make top-level JSON wrappers
    Add --{open,close}-{list,instace} options
    Add xo_xml_leader(), to detect use of some bogus XML tags. It's still bad form, but it's a little safer now
    Avoid call to xo_write before xo_flush, since the latter calls the former
    Check return code from xo_flush_h properly (<0) (FreeBSD Bug 236935)
    For JSON output, avoid newline before a container's close brace (#62)
    Merge branch 'text_only' of https://github.com/zvr/libxo into zvr-text_only
    Use XO_USE_INT_RETURN_CODES, not USE_INT_RETURN_CODES
    add docs for --continuation
    add docs for --not-first
    call xo_state_set_flags before values and close containers; add XOIF_MADE_OUTPUT flag to track state; make proper empty JSON objects in xo_finish
    color_map code has to be #ifdef'd out, since the struct definition
    correct xo_flush_func_t (doesn't use xo_ssize_t)
    make depth change for --top-wrap only for JSON
    fix to handle --top-wrap in "xo" by being more consistent with handling trailing newlines
    fix to handle text-only version #64 (from zvr)
    fix xo_buf_has_room for round up to the next XO_BUFSIZ, not just add XO_BUFSIZ to the size (FreeBSD Bug 236937)
    update docs for new "xo" options
    update functions to use xo_ssize_t
    update test cases
from 1.0.1:
    Add EINTEGRITY to .pot files under test/gettext/ (fix from FreeBSD)
from 1.0.2:
    handle failure from xo_vnsprintf; don't add -1 to "rc"

PR:		236937, 236935
Submitted by:	phil
Reported by:	Alfonso S. Siciliano <alfix86@gmail.com>
MFC after:	2 weeks