[clang] [dataflow] Add global condition to DataflowAnalysisContext (PR #65949)

[Gábor Horváth via cfe-commits]

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@@ -108,6 +108,16 @@ class DataflowAnalysisContext {
   /// A null `PointeeType` can be used for the pointee of `std::nullptr_t`.
   PointerValue &getOrCreateNullPointerValue(QualType PointeeType);
 
+  /// Adds `Constraint` to current and future flow conditions in this context.
+  ///
+  /// The global condition must contain only flow-insensitive information, i.e.
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Xazax-hun wrote:

I wonder if `GlobalConstraint` is a bit vague. How about something like `addFlowInsensitiveInvariant`. This makes part of the comment unnecessary. 

https://github.com/llvm/llvm-project/pull/65949