Re: dtc: Improve support for string escapes

So, like, the other day David Gibson mumbled:

dtc supports the use of C-style escapes (\n, \t and so forth) in
string property definitions via the data_copy_escape_string()
function.  However, while it supports the most common escape
characters, it doesn't support the full set that C does, which is a
potential gotcha.

Worse, a bug in the lexer means that while data_copy_escape_string()
can handle the \" escape, a string with such an escape won't lex
correctly.

This patch fixes both problems, extending data_copy_escape_string() to
support the missing escapes, and fixing the regex for strings in the
lexer to handle internal escaped quotes.

This also adds a testcase for string escape functionality.

Signed-off-by: David Gibson <redacted>

Excellent.  Thanks.

Applied, modulo fixing that typo.

jdl