Fix CString compatibility with bincode v1

[ZoeyR]

No description provided.

[codecov]

Codecov Report

Merging #502 (90b6786) into trunk (6c7be9c) will increase coverage by 0.02%.
The diff coverage is 90.90%.

@@            Coverage Diff             @@
##            trunk     #502      +/-   ##
==========================================
+ Coverage   69.07%   69.09%   +0.02%     
==========================================
  Files          43       44       +1     
  Lines        3056     3058       +2     
==========================================
+ Hits         2111     2113       +2     
  Misses        945      945              

Impacted Files	Coverage Δ
src/error.rs	0.00% <ø> (ø)
tests/issues/issue_498.rs	80.00% <80.00%> (ø)
src/features/impl_std.rs	78.23% <100.00%> (-0.44%)	⬇️
tests/std.rs	100.00% <100.00%> (ø)
src/de/decoder.rs	70.00% <0.00%> (+5.00%)	⬆️

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