[awk]: fails to recognize some escape sequences in strings

[inejge]

Tested with 7c928a3. The following script:

$1 == "\\"

will produce the error:

 --> /tmp/s.awk:1:7
  |
1 | $1 == "\\"
  |       ^---
  |
  = expected string, ere, number, func_name, builtin_function_call, pre_inc, pre_dec, not, unary_plus, negate, or lvalue

Likewise, the script:

$1 == "\""

will produce:

 --> 1:7
  |
1 | $1 == "\""
  |       ^--^
  |
  = invalid escape sequence

Interestingly, the error for the second script fails to report the script name (it was /tmp/s.awk in both cases.)