Update innoextract to 1.8

Summary:
Changelog:

• Added support for Inno Setup 6.0.0 installers.
• Added support for pre-release Inno Setup 5.6.2 installers used by GOG.
• Added support for two modified Inno Setup 5.5.7 variants.
• Added support for Inno Setup 1.3.0 to 1.3.23.
• Added support for My Inno Setup Extensions installers older than 3.0.6.1.
• Added support for modified Inno Setup variants using an alternative setup loader magic.
• Added support for using boost_{zlib,bzip2} when statically linking Boost.
• Added support for automatically reading external setup.0 files.
• Encoding for non-Unicode installers is now determined from the languages supported by the installer, overridable using the --codepage option.
• Implemented parsing of GOG Galaxy architecture constraints.
• The architecture-specific suffixes @32bit and @64bit are now used to disambiguate colliding files.
• Fixed output path for files with absolute paths (canonicalization now strips all unsafe characters).
• Fixed output directory being created even when not extracting files.
• Fixed a hang when using the --language option.
• Improved checksum verification for files reconstructed from GOG Galaxy file parts.
• Changed header parsing to select the first version without warnings and failing that the first without errors.
• Changed filesystem and output encoding to WTF-8 (extended UTF-8) to represent broken UTF-16 data.

Test Plan:

1. Extracted files from HoMM3 installer from GOG (packaged with Inno Setup 5.6.2 according to innoextract).
2. Extracted files fom Morrowind installer (Inno Setup 5.5.0).

Reviewers: Triage Team, JoshStrobl

Reviewed By: Triage Team, JoshStrobl

Subscribers: JoshStrobl

Differential Revision: https://dev.getsol.us/D7217