Steps needed to use reflex instead of flex...
Note that there  is additional work required to get the Scanner class working.  This just gets you some of the way:

* Delete `FlexLexer.h`
* In `aprepro_parser.h`:
  -- Add `#include "aprepro_parser.h"`
  -- Change include of `FlexLexer.h` to `reflex/flexlexer.h`
  -- the `int` arguments on LexerOutput and LexerInput are `size_t`

In aprepro.ll:

* Rename `echo` to `do_echo`
* Add `#undef yyterminate` before `#define yyterminate()`
* Add `#undef YY_USER_ACTION` before the `#define YY_USER_ACTION`

* Add:
```
%option namespace=SEAMS
%option lexer=SEAMSFlexLexer
%option lex=yylex
```
In the `/*** Fex Declarations and Options ***/` section.

* Change `%START` to `%s`

* All matching rules need to have the leading whitespace removed...  For example,
```
 <VERBATIM>{
  "{VERBATIM(OFF)}" { BEGIN(INITIAL);   }
  [A-Za-z0-9_ ]* |
    .               { if (echo) ECHO; }
    "\n"            { if (echo) ECHO; aprepro.ap_file_list.top().lineno++; }
}
```
Becomes:
```
<VERBATIM>{
"{VERBATIM(OFF)}" { BEGIN(INITIAL);   }
[A-Za-z0-9_ ]* |
.               { if (do_echo) ECHO; }
"\n"            { if (do_echo) ECHO; aprepro.ap_file_list.top().lineno++; }
}
```


This will get you part of the way to using reflex.  
