Because gal2c generates some C++ sources that do not match our coding
convention and should not be checked.
* tests/sanity/80columns.test, tests/sanity/style.test: Do not test
files in tests' work directories.
* tests/sanity/80columns.test, tests/sanity/includes.test,
tests/sanity/private.test, tests/sanity/style.test: Have each test
record failure in a separate file.