Write to file
This block allows user to save data in a file, in formatted and binary
mode. Each call to the block corresponds to a record in the file. Each
record has the following form:  [t,V1,...,Vn]  where  t  is the value
of time when block is called and Vi  is the ith input value.
The pair block is RFILE.
  
- Input size 
 a scalar. This fixes the input size.
 Properties : Type 'vec' of size 1.
 
- Output file name 
 a character string defining the path of the file.
 Properties : Type 'str' of size 1.
 
- Output Format 
 a character string defining the Fortran format
	to use or nothing for an unformatted (binary) write. If given, the
	format must began by a left parenthesis and end by a right
	parenthesis. example: (e10.3).
 Properties : Type 'str' of size 1.
 
- Buffer size 
 To improve efficiency it is possible to buffer
        the input data. Write on the file is only done after each 
        Buffer size call to the block.
 Properties : Type 'vec' of size 1.
- always active: no
- direct-feedthrough: yes
- zero-crossing: no
- mode: no
- regular inputs:
 - port 1 : size [1,1] / type 1
 
- number/sizes of activation inputs: 1
- number/sizes of activation outputs: 0
- continuous-time state: no
- discrete-time state: yes
- object discrete-time state: no
- name of computational function: writef4