Fixes syntax errors when trying to render pprof profiles that have
double quotes in tags. These can be created with Go's pprof labels
feature, for example with:

Fixes syntax errors when trying to render pprof profiles that have
double quotes in tags. These can be created with Go's pprof labels
feature, for example with:

pprof.Labels("key", "label \"double quote\"\nline two")

Trying to display a graph generated with this lable will fail:

Error: <stdin>: syntax error in line 5 near 'quote'

The double quote (") was never escaped in the label strings. Add
a new escaping function that replaces newlines with centered lines
(\n) because the existing one replaces newline with left-justified
lines (\l).