Add support for module initializers

Author: RexJaeschke

standard/portability-issues.md

@@ -44,6 +44,7 @@ A conforming implementation is required to document its choice of behavior in ea
 1. The impact of thread termination when a thread has no handler for an exception, and the thread is itself terminated. ([§13.10.6](statements.md#13106-the-throw-statement))
 1. The mechanism by which linkage to an external method is achieved. ([§15.6.8](classes.md#1568-external-methods))
 1. The impact of thread termination when no matching `catch` clause is found for an exception and the code that initially started that thread is reached. ([§22.4](exceptions.md#224-how-exceptions-are-handled)).
+1. The order of execution of module initializers in a module (§module-init-attr).
 1. An execution environment may provide additional attributes that affect the execution of a C# program. ([§23.5.1](attributes.md#2351-general))
 1. The mappings between pointers and integers. ([§24.5.1](unsafe-code.md#2451-general))
 1. The effect of applying the unary `*` operator to a `null` pointer. ([§24.6.2](unsafe-code.md#2462-pointer-indirection))