Add support for 32-bit systems

[kimikage]

This fixes #28.

~This also fixes the potential stack overflow of status(). However, flamegraph!() can still cause a stack overflow. So, we can also remove the change from this PR.~

Profiling on 32-bit systems seems to be "somewhat" different than on 64-bit systems.

[codecov[bot]]

Codecov Report

Merging #30 into master will increase coverage by 0.02%. The diff coverage is 87.50%.

@@            Coverage Diff             @@
##           master      #30      +/-   ##
==========================================
+ Coverage   96.53%   96.56%   +0.02%     
==========================================
  Files           5        5              
  Lines         231      233       +2     
==========================================
+ Hits          223      225       +2     
  Misses          8        8              

Impacted Files	Coverage Δ
src/graph.jl	97.61% <80.00%> (+0.02%)	:arrow_up:
src/io.jl	98.03% <100.00%> (+0.03%)	:arrow_up:

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[kimikage]

If https://github.com/JuliaLang/julia/issues/35870 is fixed,, the tests on x86 may show the warning. However, I haven't been able to identify the reason why so many instruction pointers stored on 32-bit system.

[timholy]

Thanks @kimikage!