enable building proper with OTP-29

[mikpe]

• eliminate old-style catches
• resolve is_record/1 ambiguity
• fix variable exported from subexpression

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 85.45%. Comparing base (f511d29) to head (af40415).
⚠️ Report is 11 commits behind head on master.

Files with missing lines	Patch %	Lines
src/proper_erlang_abstract_code.erl	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #324      +/-   ##
==========================================
+ Coverage   85.27%   85.45%   +0.18%     
==========================================
  Files          14       14              
  Lines        4590     4594       +4     
==========================================
+ Hits         3914     3926      +12     
+ Misses        676      668       -8     

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