Update .gitignore files.

Update .gitignore files to ignore Unix executables and intermediate files.

extras/.gitignore:
    ignore *.beams

extras/cgi/.gitignore:
extras/gator/.gitignore:
extras/graphics/mercury_cairo/tutorial/.gitignore:
extras/logged_output/.gitignore:
extras/monte/.gitignore:
extras/odbc/.gitignore:
extras/posix/samples/.gitignore:
extras/quickcheck/.gitignore:
extras/quickcheck/tutes/.gitignore:
extras/references/samples/.gitignore:
    ignore executable(s)

extras/references/tests/.gitignore:
extras/trailed_update/tests/.gitignore:
    ignore test *.res and *.out files,
    ignore executable

extras/windows_installer_generator/sample/.gitignore:
samples/concurrency/dining_philosophers/.gitignore:
samples/concurrency/midimon/.gitignore:
    ignore executables

tests/hard_coded/.gitignore:
    ignore *.o and *.obj object files