Add clang-format on/off around test "lines"
Run clang-format without breaking string literals:
clang-format --style='{BasedOnStyle: llvm, BreakStringLiterals: false}'
-i test_demangle.pass.cpp
Add clang-format on/off on fp_literal_cases
Fixups: Split UNSUPPORTED to next line; xfail_cases trailing comma
Replace physical tab