Add deftype

[water111]

Adds a parser for deftype type definitions in the common library, and moving GOOS to the common library to support this.

The deftype parser has some optional assert features which let you specify where fields should be in the type layout, where methods should be in the method table, the size of the type, and what the GOAL type flags should be. If the compiler comes up with a different result, it'll throw a compiler error. We can use this to make sure that our memory layout matches the original and that OpenGOAL's behavior matches the original compiler.

Also adds deftype to the compiler, including calling the new_type function in the runtime.

Adds bfloat's deftype to gcommon.gc.

[coveralls]

Pull Request Test Coverage Report for Build 260348970

• 234 of 299 (78.26%) changed or added relevant lines in 13 files are covered.
• 50 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+2.07%) to 61.811%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
common/type_system/Type.cpp	0	1	0.0%
goalc/compiler/Compiler.cpp	0	1	0.0%
goalc/compiler/IR.cpp	16	17	94.12%
goalc/compiler/compilation/Function.cpp	0	2	0.0%
goalc/compiler/compilation/Type.cpp	21	23	91.3%
goalc/compiler/Val.h	3	6	50.0%
common/type_system/deftype.cpp	149	204	73.04%

Files with Coverage Reduction	New Missed Lines	%
goalc/compiler/Compiler.cpp	11	61.07%
goalc/emitter/IGen.h	39	92.85%

Totals
Change from base Build 256519513:	2.07%
Covered Lines:	13162
Relevant Lines:	21294

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💛 - Coveralls