C++ namespace cleanup (except tests).

libsolidity/analysis/PostTypeChecker.h

@@ -23,15 +23,13 @@
 #include <libsolidity/ast/ASTForward.h>
 #include <libsolidity/ast/ASTVisitor.h>
 
-namespace langutil
+namespace solidity::langutil
 {
 class ErrorReporter;
 struct SourceLocation;
 }
 
-namespace dev
-{
-namespace solidity
+namespace solidity::frontend
 {
 
 /**
@@ -93,4 +91,3 @@ private:
 };
 
 }
-}