Update to Rodin 3.8 sources

META-INF/MANIFEST.MF

build.gradle

src/org/eventb/core/ast/ExtendedPredicate.java

src/org/eventb/core/ast/FreeIdentifier.java

src/org/eventb/core/ast/ITypeEnvironment.java

...ventb/internal/core/ast/datatype/DatatypeTranslation.java

...ntb/internal/core/ast/extension/ExtensionTranslation.java

src/org/eventb/internal/core/typecheck/TypeEnvironment.java