Work around another MergeModules crash (apple#62)

* [utils] Add utility for shuffling sources to help reproduce MergeModules issues

* [Deque] Collapse Sequence/Collection conformances into a single file

The MergeModules phase in the compiler is broken: it isn’t always able to correctly handle circular dependencies across source files, like the ones that keep organically popping up with Sequence/Collection conformances that are defined in separate files.

Such dependencies sometimes triggers a compiler crash, depending on some (unknown) environmental parameters.

Trying to manually find and eliminate these circular dependencies has not proved productive. Instead, roll all Collection conformances into a single, huge source file.

* [Deque] Update CMakeLists

Author: lorentey

Sources/DequeModule/CMakeLists.txt

@@ -17,17 +17,14 @@ add_library(DequeModule
   Deque._UnsafeHandle.swift
   Deque.swift
   Deque+Codable.swift
+  Deque+Collection.swift
   Deque+CustomDebugStringConvertible.swift
   Deque+CustomReflectable.swift
   Deque+CustomStringConvertible.swift
   Deque+Equatable.swift
   Deque+ExpressibleByArrayLiteral.swift
   Deque+Extras.swift
   Deque+Hashable.swift
-  Deque+MutableCollection.swift
-  Deque+RandomAccessCollection.swift
-  Deque+RangeReplaceableCollection.swift
-  Deque+Sequence.swift
   Deque+Testing.swift
   UnsafeMutableBufferPointer+Utilities.swift)
 set_target_properties(DequeModule PROPERTIES