Drop support for Swift 5.9 (#845)

Author: glbrntt

.github/workflows/main.yml

@@ -11,7 +11,6 @@ jobs:
         name: Unit tests
         uses: apple/swift-nio/.github/workflows/unit_tests.yml@main
         with:
-            linux_5_9_enabled: false
             linux_5_10_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
             linux_6_0_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
             linux_6_1_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"

.github/workflows/pull_request.yml

@@ -14,7 +14,6 @@ jobs:
         name: Unit tests
         uses: apple/swift-nio/.github/workflows/unit_tests.yml@main
         with:
-            linux_5_9_enabled: true
             linux_5_10_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
             linux_6_0_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"
             linux_6_1_arguments_override: "--explicit-target-dependency-import-check error -Xswiftc -warnings-as-errors"

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.9
+// swift-tools-version:5.10
 //===----------------------------------------------------------------------===//
 //
 // This source file is part of the AsyncHTTPClient open source project

README.md

@@ -306,7 +306,7 @@ Please have a look at [SECURITY.md](SECURITY.md) for AsyncHTTPClient's security
 
 ## Supported Versions
 
-The most recent versions of AsyncHTTPClient support Swift 5.9 and newer. The minimum Swift version supported by AsyncHTTPClient releases are detailed below:
+The most recent versions of AsyncHTTPClient support Swift 5.10 and newer. The minimum Swift version supported by AsyncHTTPClient releases are detailed below:
 
 AsyncHTTPClient     | Minimum Swift Version
 --------------------|----------------------
@@ -317,4 +317,5 @@ AsyncHTTPClient     | Minimum Swift Version
 `1.18.0 ..< 1.20.0` | 5.6
 `1.20.0 ..< 1.21.0` | 5.7
 `1.21.0 ..< 1.26.0` | 5.8
-`1.26.0 ...`        | 5.9
+`1.26.0 ..< 1.27.0` | 5.9
+`1.27.0 ...`        | 5.10

Sources/AsyncHTTPClient/HTTPClient+HTTPCookie.swift

@@ -216,21 +216,12 @@ extension String.UTF8View.SubSequence {
     }
 }
 
-#if compiler(>=5.10)
 nonisolated(unsafe) private let posixLocale: UnsafeMutableRawPointer = {
     // All POSIX systems must provide a "POSIX" locale, and its date/time formats are US English.
     // https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap07.html#tag_07_03_05
     let _posixLocale = newlocale(LC_TIME_MASK | LC_NUMERIC_MASK, "POSIX", nil)!
     return UnsafeMutableRawPointer(_posixLocale)
 }()
-#else
-private let posixLocale: UnsafeMutableRawPointer = {
-    // All POSIX systems must provide a "POSIX" locale, and its date/time formats are US English.
-    // https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap07.html#tag_07_03_05
-    let _posixLocale = newlocale(LC_TIME_MASK | LC_NUMERIC_MASK, "POSIX", nil)!
-    return UnsafeMutableRawPointer(_posixLocale)
-}()
-#endif
 
 private func parseTimestamp(_ utf8: String.UTF8View.SubSequence, format: String) -> tm? {
     var timeComponents = tm()