Add literals for fast types

[mborland]

Closes: #751

Also fixes the range of dec32_fast being slightly larger than it should be, and a typo in the dec32 literals docs

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.1%. Comparing base (c21c6b7) to head (71ed999).
Report is 14 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop    #753     +/-   ##
=========================================
+ Coverage     99.1%   99.1%   +0.1%     
=========================================
  Files          227     227             
  Lines        16759   16797     +38     
  Branches      1807    1808      +1     
=========================================
+ Hits         16605   16643     +38     
  Misses         154     154             

Files with missing lines	Coverage Δ
include/boost/decimal/decimal32_fast.hpp	96.8% <100.0%> (ø)
include/boost/decimal/literals.hpp	100.0% <ø> (ø)
test/test_literals.cpp	100.0% <100.0%> (ø)

... and 1 file with indirect coverage changes

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