Hardened String Block Parser

[iBotPeaches]

• Supports when string block header is packed w/ extra data.
• Supports when string block has style count == 0, but style offset > 0
• Supports when extra data remaining after reading strings or styles
• Supports when string block has more strings than can fit

fixes: #3236

[iBotPeaches]

Nevermind - this isn't ready. Regressed the sample app with style count = 0, but style offset > 0.

[iBotPeaches]

07-31 05:44:57.579 283041 283041 W ResourceType: Bad string block: string #316 entry is at 6488080, past end at 21420

Missing one more patch. Need to handle when string block has more strings reported than can fit.