Hi,

there still seem to be some subtle issues with detection of raw string
literals. Unfortunately they are hard to reproduce. One example that fails
(for me) with a recent master build is:

cd /tmp
wget
https://raw.githubusercontent.com/google/protobuf/ef7894e2dc6d287419e42a4fdc52cdfedd386d16/conformance/conformance_test.cc
/path/to/emacs -Q +686 conformance_test.cc

Around that line the fontification of the raw string literals is wrong
(quote characters are treated as string terminators), in other parts of the
file the fontification is correct. This typically happens with files that
contain many large raw string literals that contain quote characters.