patch 8.0.0170: crash in channel test

Problem:    Channel test fails for using freed memory.
Solution:   Fix memory use in json_decode().

patch 8.0.0169: json_decode() may run out of stack space

Problem:    For complicated string json_decode() may run out of stack space.
Solution:   Change the recursive solution into an iterative solution.

patch 8.0.0168: not all float functionality is tested

Problem:    Still some float functionality is not covered by tests.
Solution:   Add more tests. (Dominique Pelle, closes vim#1364)

patch 8.0.0167: str2nr()/str2float() fail with negative values

Problem:    str2nr() and str2float() do not always work with negative values.
Solution:   Be more flexible about handling signs. (LemonBoy, closes vim#1332)
            Add more tests.

patch 8.0.0166: JSON with a duplicate key gives an internal error

Problem:    JSON with a duplicate key gives an internal error. (Lcd)
Solution:   Give a normal error.  Avoid an error when parsing JSON from a
            remote client fails.

patch 8.0.0165: ubsan warns for integer overflow

Problem:    Ubsan warns for integer overflow.
Solution:   Swap two conditions. (Dominique Pelle)

patch 8.0.0164: outdated and misplaced comments

Problem:    Outdated and misplaced comments.
Solution:   Fix the comments.

patch 8.0.0163: cannot build with Ruby 2.4

Problem:    Ruby 2.4 no longer supports rb_cFixnum.
Solution:   move rb_cFixnum into an #ifdef. (Kazuki Sakamoto, closes vim#1365)

patch 8.0.0162: build error on Fedora 23

Problem:    Build error on Fedora 23 with small features and gnome2.
Solution:   Undefine ngettext(). (Hirohito Higashi)

patch 8.0.0161: can't build with small features

Problem:    Build fails when using small features.
Solution:   Update #ifdef for using save_ccline. (Hirohito Higashi)