Resolve availability warnings / fix non-Darwin build

Author: jmschonfeld

Sources/FoundationEssentials/Data/Data+Deprecated.swift

@@ -10,6 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+@available(macOS 10.10, iOS 8.0, watchOS 2.0, tvOS 9.0, *)
 extension Data {
     @available(swift, introduced: 4.2)
     @available(swift, deprecated: 5, message: "use `init(_:)` instead")

Sources/FoundationEssentials/Data/Data+Iterator.swift

@@ -10,6 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+@available(macOS 10.10, iOS 8.0, watchOS 2.0, tvOS 9.0, *)
 extension Data {
     /// An iterator over the contents of the data.
     ///

Sources/FoundationEssentials/Data/Data+Reading.swift

@@ -514,6 +514,7 @@ private func readBytesFromFileDescriptor(_ fd: Int32, path: PathOrURL, buffer in
     return length - numBytesRemaining
 }
 
+@available(macOS 10.10, iOS 8.0, watchOS 2.0, tvOS 9.0, *)
 extension Data {
 #if FOUNDATION_FRAMEWORK
     public typealias ReadingOptions = NSData.ReadingOptions

Sources/FoundationEssentials/Data/Data+Searching.swift

@@ -10,6 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+@available(macOS 10.10, iOS 8.0, watchOS 2.0, tvOS 9.0, *)
 extension Data {
 #if FOUNDATION_FRAMEWORK
     public typealias SearchOptions = NSData.SearchOptions

Sources/FoundationEssentials/Data/Data+Writing.swift

@@ -722,6 +722,7 @@ private func writeExtendedAttributes(fd: Int32, attributes: [String : Data]) {
 }
 #endif // !NO_FILESYSTEM
 
+@available(macOS 10.10, iOS 8.0, watchOS 2.0, tvOS 9.0, *)
 extension Data {
 #if FOUNDATION_FRAMEWORK
     public typealias WritingOptions = NSData.WritingOptions

Sources/FoundationEssentials/Data/Representations/Data+Inline.swift

@@ -10,6 +10,17 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if canImport(Glibc)
+@preconcurrency import Glibc
+#elseif canImport(Musl)
+@preconcurrency import Musl
+#elseif canImport(ucrt)
+import ucrt
+#elseif canImport(WASILibc)
+@preconcurrency import WASILibc
+#endif
+
+@available(macOS 10.10, iOS 8.0, watchOS 2.0, tvOS 9.0, *)
 extension Data {
     // A small inline buffer of bytes suitable for stack-allocation of small data.
     // Inlinability strategy: everything here should be inlined for direct operation on the stack wherever possible.

Sources/FoundationEssentials/Data/Representations/Data+InlineSlice.swift

@@ -10,6 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+@available(macOS 10.10, iOS 8.0, watchOS 2.0, tvOS 9.0, *)
 extension Data {
 #if _pointerBitWidth(_64)
     @usableFromInline internal typealias HalfInt = Int32

Sources/FoundationEssentials/Data/Representations/Data+LargeSlice.swift

@@ -10,6 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+@available(macOS 10.10, iOS 8.0, watchOS 2.0, tvOS 9.0, *)
 extension Data {
     // A reference wrapper around a Range<Int> for when the range of a data buffer is too large to whole in a single word.
     // Inlinability strategy: everything should be inlinable as trivial.

Sources/FoundationEssentials/Data/Representations/Data+Representation.swift

@@ -10,6 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+@available(macOS 10.10, iOS 8.0, watchOS 2.0, tvOS 9.0, *)
 extension Data {
     // The actual storage for Data's various representations.
     // Inlinability strategy: almost everything should be inlinable as forwarding the underlying implementations. (Inlining can also help avoid retain-release traffic around pulling values out of enums.)

Sources/FoundationEssentials/Data/Representations/DataStorage.swift

@@ -10,6 +10,16 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if canImport(Glibc)
+@preconcurrency import Glibc
+#elseif canImport(Musl)
+@preconcurrency import Musl
+#elseif canImport(ucrt)
+import ucrt
+#elseif canImport(WASILibc)
+@preconcurrency import WASILibc
+#endif
+
 // Underlying storage representation for medium and large data.
 // Inlinability strategy: methods from here should not inline into InlineSlice or LargeSlice unless trivial.
 // NOTE: older overlays called this class _DataStorage. The two must