OSV-2020-1456 Segv on unknown address in clang::SourceManager::getFileIDLoaded

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=19205 Crash type: Segv on unknown address Crash state: clang::SourceManager::getFileIDLoaded clang::SourceManager::isAtEndOfImmediateMacroExpansion clang::Lexer::isAtEndOfMacroExpansion...