[decompiler] Small bitfield fixes

[water111]

• When doing a (set! some-bitfield-var some-expr), it will attempt to convert some-expr to a bitfield def if possible.
• If a bitfield def fails, will fall back to a cast in more cases.
• Fixed a bug with types from accessing bitfields causing extra casts and sometimes errors.
• Made stack slot store/load much less strict to work around GOAL compiler bugs.
• Added missing case for inline-array access. Seems to be used when a symbol is an inline-array

[coveralls]

Pull Request Test Coverage Report for Build 944770677

• 49 of 61 (80.33%) changed or added relevant lines in 5 files are covered.
• 5 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.003%) to 69.312%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
decompiler/IR2/FormExpressionAnalysis.cpp	30	31	96.77%
decompiler/IR2/bitfields.cpp	6	8	75.0%
decompiler/util/data_decompile.cpp	3	7	42.86%
decompiler/IR2/AtomicOpTypeAnalysis.cpp	2	7	28.57%

Files with Coverage Reduction	New Missed Lines	%
decompiler/IR2/FormExpressionAnalysis.cpp	1	79.98%
decompiler/IR2/Form.cpp	2	73.34%
decompiler/IR2/FormStack.cpp	2	78.99%

Totals
Change from base Build 944729300:	0.003%
Covered Lines:	36465
Relevant Lines:	52610

---

💛 - Coveralls