Add MAPI definitions for Message-ID and In-Reply-To

[JanSkalny]

Summary

Add support for reading and exporting the Internet Message-ID and In-Reply-To MAPI properties.

Changes

• Define LIBPFF_ENTRY_TYPE_INTERNET_MESSAGE_ID and LIBPFF_ENTRY_TYPE_IN_REPLY_TO_ID
• Add UTF-8 and UTF-16 convenience accessor macros
• Include Message-ID and In-Reply-To in pffexport message header output

[joachimmetz]

Thanks for the proposed changes, you might need to rebase with HEAD given you submitted the PR while I was making some changes.

I'll take a close look as soon as time permits

[codecov]

Codecov Report

❌ Patch coverage is 0% with 63 lines in your changes missing coverage. Please review.
✅ Project coverage is 23.66%. Comparing base (6148c9e) to head (1fdbe53).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
libpff/libpff_folder.c	0.00%	22 Missing ⚠️
pfftools/export_handle.c	0.00%	18 Missing ⚠️
pfftools/item_file.c	0.00%	18 Missing ⚠️
libpff/libpff_huffman_tree.c	0.00%	2 Missing and 1 partial ⚠️
libpff/libpff_record_entry.c	0.00%	1 Missing ⚠️
libpff/libpff_table.c	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #159      +/-   ##
==========================================
+ Coverage   23.55%   23.66%   +0.10%     
==========================================
  Files          62       62              
  Lines       20629    20477     -152     
  Branches     4958     4963       +5     
==========================================
- Hits         4859     4845      -14     
+ Misses      14657    14520     -137     
+ Partials     1113     1112       -1     

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