more header reductions and forward declarations

[neheb]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 64.28571% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.77%. Comparing base (79e253f) to head (d5c4155).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/tiffcomposite_int.cpp	56.52%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3408      +/-   ##
==========================================
- Coverage   64.78%   64.77%   -0.02%     
==========================================
  Files         103      103              
  Lines       21697    21691       -6     
  Branches    10646    10646              
==========================================
- Hits        14057    14050       -7     
  Misses       5419     5419              
- Partials     2221     2222       +1     

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