Let the 9.4 migrator migrate the Swift source.

No changes were needed, but since the Xcode projects pick up the updated
setting, the tests require a newer Xcode that supports Swift 4.

This is being done because Xcode 10 starting warning about Swift 3 support
going away in the future, so we might as well do the updates since most
folks shouldn't be on those really old Xcode versions any more.

objectivec/DevTools/full_mac_build.sh

@@ -239,27 +239,11 @@ if [[ "${DO_XCODE_IOS_TESTS}" == "yes" ]] ; then
   # just pick a mix of OS Versions and 32/64 bit.
   # NOTE: Different Xcode have different simulated hardware/os support.
   case "${XCODE_VERSION}" in
-    6.* )
-      echo "ERROR: Xcode 6.3/6.4 no longer supported for building, please use 8.0 or higher." 1>&2
-      exit 10
-      ;;
-    7.* )
-      echo "ERROR: Xcode 7.x no longer supported for building, please use 8.0 or higher." 1>&2
+    [6-8].* )
+      echo "ERROR: The unittests include Swift code that is now Swift 4.0." 1>&2
+      echo "ERROR: Xcode 9.0 or higher is required to build the test suite, but the library works with Xcode 7.x." 1>&2
       exit 11
       ;;
-    8.0* )
-      # The 8.* device seem to hang and never start under Xcode 8.
-      XCODEBUILD_TEST_BASE_IOS+=(
-          -destination "platform=iOS Simulator,name=iPhone 4s,OS=9.0" # 32bit
-          -destination "platform=iOS Simulator,name=iPhone 7,OS=10.0" # 64bit
-      )
-      ;;
-    8.[1-3]* )
-      XCODEBUILD_TEST_BASE_IOS+=(
-          -destination "platform=iOS Simulator,name=iPhone 4s,OS=8.1" # 32bit
-          -destination "platform=iOS Simulator,name=iPhone 7,OS=latest" # 64bit
-      )
-      ;;
     9.[0-2]* )
       XCODEBUILD_TEST_BASE_IOS+=(
           -destination "platform=iOS Simulator,name=iPhone 4s,OS=8.1" # 32bit
@@ -317,13 +301,9 @@ if [[ "${DO_XCODE_OSX_TESTS}" == "yes" ]] ; then
     XCODEBUILD_TEST_BASE_OSX+=( -quiet )
   fi
   case "${XCODE_VERSION}" in
-    6.* )
-      echo "ERROR: Xcode 6.3/6.4 no longer supported for building, please use 8.0 or higher." 1>&2
-      exit 10
-      ;;
-    7.* )
-      echo "ERROR: The unittests include Swift code that is now Swift 3.0." 1>&2
-      echo "ERROR: Xcode 8.0 or higher is required to build the test suite, but the library works with Xcode 7.x." 1>&2
+    [6-8].* )
+      echo "ERROR: The unittests include Swift code that is now Swift 4.0." 1>&2
+      echo "ERROR: Xcode 9.0 or higher is required to build the test suite, but the library works with Xcode 7.x." 1>&2
       exit 11
       ;;
   esac

objectivec/ProtocolBuffers_OSX.xcodeproj/project.pbxproj

@@ -640,7 +640,7 @@
 				LastUpgradeCheck = 0930;
 				TargetAttributes = {
 					8BBEA4A5147C727100C4ADB7 = {
-						LastSwiftMigration = 0800;
+						LastSwiftMigration = 0940;
 						TestTargetID = 8B9A5EA41831993600A9D33B;
 					};
 					F45BBC141B0CE3C6002D064D = {
@@ -852,7 +852,7 @@
 				PRODUCT_NAME = UnitTests;
 				SWIFT_OBJC_BRIDGING_HEADER = "Tests/UnitTests-Bridging-Header.h";
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
-				SWIFT_VERSION = 3.0;
+				SWIFT_VERSION = 4.0;
 				WARNING_CFLAGS = (
 					"$(inherited)",
 					"-Wno-documentation-unknown-command",
@@ -878,7 +878,7 @@
 				PRODUCT_BUNDLE_IDENTIFIER = "com.yourcompany.${PRODUCT_NAME:identifier}";
 				PRODUCT_NAME = UnitTests;
 				SWIFT_OBJC_BRIDGING_HEADER = "Tests/UnitTests-Bridging-Header.h";
-				SWIFT_VERSION = 3.0;
+				SWIFT_VERSION = 4.0;
 				WARNING_CFLAGS = (
 					"$(inherited)",
 					"-Wno-documentation-unknown-command",

objectivec/ProtocolBuffers_iOS.xcodeproj/project.pbxproj

@@ -647,7 +647,7 @@
 				LastUpgradeCheck = 0930;
 				TargetAttributes = {
 					8BBEA4A5147C727100C4ADB7 = {
-						LastSwiftMigration = 0800;
+						LastSwiftMigration = 0940;
 						TestTargetID = 8B9A5EA41831993600A9D33B;
 					};
 					F45BBC0E1B0CDB50002D064D = {
@@ -866,7 +866,7 @@
 				PRODUCT_NAME = UnitTests;
 				SWIFT_OBJC_BRIDGING_HEADER = "Tests/UnitTests-Bridging-Header.h";
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
-				SWIFT_VERSION = 3.0;
+				SWIFT_VERSION = 4.0;
 				TARGETED_DEVICE_FAMILY = "1,2";
 				WARNING_CFLAGS = (
 					"$(inherited)",
@@ -900,7 +900,7 @@
 				OTHER_LDFLAGS = "-ObjC";
 				PRODUCT_NAME = UnitTests;
 				SWIFT_OBJC_BRIDGING_HEADER = "Tests/UnitTests-Bridging-Header.h";
-				SWIFT_VERSION = 3.0;
+				SWIFT_VERSION = 4.0;
 				TARGETED_DEVICE_FAMILY = "1,2";
 				WARNING_CFLAGS = (
 					"$(inherited)",