Clang importer: use lookup table version number in the module file extension hash.

We were verifying the Swift full version information from the module
file extension metadata for the Swift name lookup tables, but not
actually putting it in the hash, which meant that having an older
module cache around would cause spurious failures when Swift name
lookup tables were enabled. Instead, use just the major/minor version
numbers of the lookup tables. When the lookup table format or contents
of the lookup table change, we'll bump the version number.

Author: DougGregor

lib/ClangImporter/ClangImporter.cpp

@@ -4464,12 +4464,11 @@ ClangImporter::Implementation::createExtensionReader(
   clang::serialization::ModuleFile &mod,
   const llvm::BitstreamCursor &stream)
 {
-  // Make sure we have a compatible block.
+  // Make sure we have a compatible block. Since these values are part
+  // of the hash, it should never be wrong.
   assert(metadata.BlockName == "swift.lookup");
-  if (metadata.MajorVersion != SWIFT_LOOKUP_TABLE_VERSION_MAJOR ||
-      metadata.MinorVersion != SWIFT_LOOKUP_TABLE_VERSION_MINOR ||
-      metadata.UserInfo != version::getSwiftFullVersion())
-    return nullptr;
+  assert(metadata.MajorVersion == SWIFT_LOOKUP_TABLE_VERSION_MAJOR);
+  assert(metadata.MinorVersion == SWIFT_LOOKUP_TABLE_VERSION_MINOR);
 
   // Check whether we already have an entry in the set of lookup tables.
   auto &entry = LookupTables[mod.ModuleName];

lib/ClangImporter/SwiftLookupTable.h

@@ -50,7 +50,7 @@ const uint16_t SWIFT_LOOKUP_TABLE_VERSION_MAJOR = 1;
 /// Lookup table major version number.
 ///
 /// When the format changes IN ANY WAY, this number should be incremented.
-const uint16_t SWIFT_LOOKUP_TABLE_VERSION_MINOR = 0;
+const uint16_t SWIFT_LOOKUP_TABLE_VERSION_MINOR = 1;
 
 /// A lookup table that maps Swift names to the set of Clang
 /// declarations with that particular name.