Fall back to `Base.bodyfunction`

[timholy]

bodymethod was the prototype for Base.bodyfunction. Now that is being updated for changes in lowering, so it's better to rely on it.

[codecov[bot]]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (3194ce0) 94.54% compared to head (5306cae) 94.08%.

Files	Patch %	Lines
src/signatures.jl	88.88%	4 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #95      +/-   ##
==========================================
- Coverage   94.54%   94.08%   -0.46%     
==========================================
  Files           5        5              
  Lines        1228     1234       +6     
==========================================
  Hits         1161     1161              
- Misses         67       73       +6     

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[timholy]

Superseded by #108