MIME Tools v3.5: add codec enhancements, UTF-16LE Base64, RFC 2047 decoding, and SAML improvements

[ExSlam]

Summary

This PR brings the accumulated MIME Tools improvements from the fork back into the upstream repository and updates the plugin to v3.5.

The changes add new Base64, Base64URL, MIME header, and SAML functionality while also improving codec performance, buffer handling, build consistency, and CI coverage.

Main changes

Base64

• Add Base64 Encode with padding by line.

• Add Base64URL Encode and Base64URL Decode.

• Add UTF-16LE Base64 Encode and Decode.

  • Useful for any UTF-16LE Base64 data, including PowerShell -EncodedCommand.
  • Addresses Feature request: Support for UTF-16 encoded Base64 #14.

• Clarify the existing per-line decoder as Base64 Decode by line (padded/unpadded).

• Optimize Base64 and Base64URL encoding/decoding.

• Make padded-by-line Base64 encoding single-pass.

MIME / RFC 2047

• Add MIME Header Decode (RFC 2047).
• Support both B (Base64) and Q encoded-words.
• Handle charset conversion into the active document code page.
• Addresses Ability to decode "encoded-word"'s #37.

Quoted-Printable

• Optimize Quoted-Printable decoding to avoid unnecessary repeated work and improve performance on larger selections.

SAML

• Fix the longstanding SAML Decode corruption issue where valid HTTP-Redirect SAML messages could decode into corrupted XML containing embedded NUL characters.

• The root cause was truncation of DEFLATE length/distance base-table values in the bundled inflater.

• Fix SAML Decode URL-error handling and a temporary Base64 buffer leak.

• Addresses UTF8 Encoding issues for SAML Decode #5.

• Add SAML Encode for the SAML 2.0 HTTP-Redirect binding:

  • raw DEFLATE
  • Base64
  • URL encoding

• Add a small dependency-free raw DEFLATE compressor for the encoding path.

• SAML Encode and Decode can now be used as inverse operations for HTTP-Redirect payloads.

Safety and implementation cleanup

• Replace several manually sized buffers with safer dynamically sized containers.
• Add overflow and bounds checks around codec operations and Scintilla selections.
• Reduce unnecessary selection and intermediate-buffer copies.
• Remove unused declarations.
• Clean up and translate comments.

Build and CI

• Make Visual Studio compile settings consistent across Win32, x64, and ARM64.

• Enable additional compiler security checks and release optimizations.

• Restore CI builds on pushes and pull requests.

• Build both Debug and Release configurations for:

  • Win32
  • x64
  • ARM64

Version

Updates MIME Tools to v3.5.

Closes #5
Closes #14
Closes #37