Better error reporting in embedded code form/expr sections.
Support verbatim tags.

Copied more or less straight off of the old scanner.

Performance doesn't seem to have been hurt at all by the addition of the verbatim tag support.

Running benchmarks for 10 seconds on 1388 bytes (bench.dtl)...
Running erlydtl_new_scanner, hold on... ok
Running erlydtl_scanner, hold on... ok
erlydtl_new_scanner scanned  33291 times in 10.000 seconds @ 4512.5 Kbytes/sec
  min 0.000 max 0.004 avg 0.000300
erlydtl_scanner scanned  22958 times in 10.000 seconds @ 3111.9 Kbytes/sec
  min 0.000 max 0.006 avg 0.000436
Deltas
  Count     :    10333.000   45.0%
  Total time:        0.000    0.0%
  Min       :        0.000      ~%
  Max       :       -0.002  -33.3%
  Avg       :       -0.000  -31.0%
  Kbytes/s  :     1400.606   45.0%
Done.