[Bug tree-optimization/70433] backslashes lost in dot file

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70433

--- Comment #1 from vries at gcc dot gnu.org ---
Created attachment 38115
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38115&action=edit
tentative patch

Using this patch, we get in the dot file:
...
printf\ (\"\\\"%s\\\"\",\ &__FUNCTION__);
...

and in the resulting graph file:
...
printf ("\"%s\"", &__FUNCTION__);
...