Revert "Migrate from UnsafePointer<Void> to UnsafeRawPointer. (#3724)"

This reverts commit ece0951924.

This results in lldb failues on linux that I can't readily debug.
Backing out until they can be resolved.

stdlib/public/core/UnsafeRawPointer.swift.gyb

@@ -27,13 +27,6 @@ public struct Unsafe${Mutable}RawPointer : Strideable, Hashable, _Pointer {
   /// Implements conformance to the public protocol `_Pointer`.
   public let _rawValue: Builtin.RawPointer
 
-  // Construct ${a_Self} from another ${a_Self}.
-  // FIXME: Why is this necessary?
-  @_transparent
-  public init(_ other: Unsafe${Mutable}RawPointer) {
-    self = other
-  }
-
   /// Convert a builtin raw pointer to ${a_Self}.
   @_transparent
   public init(_ _rawValue: Builtin.RawPointer) {
@@ -165,7 +158,6 @@ public struct Unsafe${Mutable}RawPointer : Strideable, Hashable, _Pointer {
   /// - Warning: Binding memory to a type is potentially undefined if the
   ///   memory is ever accessed as an unrelated type.
   @_transparent
-  @discardableResult
   public func bindMemory<T>(to type: T.Type, capacity count: Int)
   -> Unsafe${Mutable}Pointer<T> {
     Builtin.bindMemory(_rawValue, count._builtinWordValue, type)