swift234

SILParser: parsing GenericParamList.

To parse GenericParamList in SILParser, we try to share code with TypeChecker.
We add handleSILGenericParams in Subsystems.h in order for SILParser to call
TypeChecker's handling of GenericParamList (this is motivated by the example of
SILParser calling performTypeLocChecking). handleSILGenericParams calls
checkGenericParamList and finalizeGenericParamList.

A Builder field (ArchetypeBuilder*) is added to GenericParamList so we can add
the same-type requirements to GenericSignature in getAsCanonicalGenericSignature
by checking SameTypeRequirements of the builder.

resolvePotentialArchetypeToType is moved from a static helper function in
TypeCheckGeneric.cpp to a public helper function in ArchetypeBuilder.cpp.
When constructing the same-type requirements in getAsCanonicalGenericSignature,
we will call it to convert from PotentialArchetype to a dependent type.

rdar://16238241


Swift SVN r14922