Update backslash_escapes.rb
Update backslash_escapes.rb

fix `"\018"` highlighting issue, which should be identified as two characters. the issue occurs in c/oc/ocpp but not in cpp.
jeff-hykin/better-cpp-syntax,jeff-hykin/better-cpp-syntax,jeff-hykin/better-cpp-syntax,jeff-hykin/better-cpp-syntax,jeff-hykin/better-cpp-syntax,jeff-hykin/better-cpp-syntax