Fix overflow issues occurs when *unchecked-math* is disabled

[alumi]

fixes: #332

This PR fixes issues found in #330 (review)

Some functions under cljam.io.cram and cljam.io.util.lsb used the checked narrowing conversions of numerical values (byte, int, ...) or implicit conversions with typed method callings of Java core library.
These narrowing of numeric types works fine as long as *unchecked-math* is set to true or only non-negative integers are involved. However, if *unchecked-math* is false (which is the default) and a negative integer is provided, an exception is thrown.
In this PR, I have explicitly applied unchecked narrowing (unchecked-byte, unchecked-int, ...) to bypass range checks and ensure the intended output.
I have also fixed the :gloval-vars option in the project to reset the compiler options while testing in CI.

I have confirmed that lein test :all passes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.95%. Comparing base (9408e13) to head (1e69b95).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #337      +/-   ##
==========================================
- Coverage   89.96%   89.95%   -0.01%     
==========================================
  Files         104      104              
  Lines        9723     9719       -4     
  Branches      529      529              
==========================================
- Hits         8747     8743       -4     
  Misses        447      447              
  Partials      529      529              

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