fix string format of unsupported MSSQL datetimeoffset (-155)

- fix format of returned object of type `DATETIMEOFFSET` (-155) from
  `"2018-09-12 22:38:56 Pacific Standard Time"` to
  `"2018-09-13 05:41:20.4607764 +00:00"`
- closes #207, "datetimeoffset unsupported" (in modern SQL Server ODBC
  drivers)

Author: Bill Evans

NEWS.md

@@ -1,3 +1,10 @@
+# odbc 1.1.6.9000
+
+- fix SQL Server ODBC's unsupported '-155' data type, and its losing
+  sub-second precision on timestamps; this still returns type
+  `DATETIMEOFFSET` as a character, but it preserves sub-seconds and
+  has a numeric timezone offset (#207, @r2evans)
+
 # odbc 1.1.6
 
 ## Features

src/nanodbc/nanodbc.cpp

@@ -2623,7 +2623,6 @@ class result::result_impl
                 break;
             case SQL_TIMESTAMP:
             case SQL_TYPE_TIMESTAMP:
-            case SQL_SS_TIMESTAMPOFFSET:
                 col.ctype_ = SQL_C_TIMESTAMP;
                 col.clen_ = sizeof(timestamp);
                 break;
@@ -2640,6 +2639,7 @@ class result::result_impl
                 break;
             case SQL_WCHAR:
             case SQL_WVARCHAR:
+            case SQL_SS_TIMESTAMPOFFSET:
                 col.ctype_ = SQL_C_WCHAR;
                 col.clen_ = (col.sqlsize_ + 1) * sizeof(SQLWCHAR);
                 if (is_blob)