Use unsigned char as the underlying type for the tribool state

[Lastique]

This makes sizeof(tribool) == 1, which is similar to sizeof(bool) on most platforms. This is only enabled when C++11 scoped enums are supported.

[mclow]

Note that sizeof(bool) == 4 on most unix systems.

[Lastique]

You mean legacy UNIX'es that are now dead? I'm only aware of Solaris on Sparc where this is true. On Linux and, I think, all BSDs, sizeof(bool) is 1. Windows, too.

[codecov]

Codecov Report

Merging #28 (d53263d) into develop (1457784) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop      #28   +/-   ##
========================================
  Coverage    97.72%   97.72%           
========================================
  Files            2        2           
  Lines          132      132           
========================================
  Hits           129      129           
  Misses           3        3           

Impacted Files	Coverage Δ
include/boost/logic/tribool.hpp	98.27% <ø> (ø)

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[jeking3]

@Lastique can you rebase on develop to get the full set of CI to run on this?

[Lastique]

@Lastique can you rebase on develop to get the full set of CI to run on this?

Done.