Stdlib: Support size in FileRead

[Shaikh-Ubaid]

Fixes the following:

% cat file_19.f90 
program file_19
    implicit none

    character(len=25) :: buffer
    integer :: chunk, iostat

    open(11, file="file_19_data.txt")
    read(11, '(a)', iostat=iostat, size=chunk, advance='no') buffer

    print *, buffer
    if (buffer /= " Hi this is 1st line!") error stop

    print *, chunk
    if (chunk /= 21) error stop

end program
% cat file_19_data.txt 
 Hi this is 1st line!
% gfortran file_19.f90 
% ./a.out 
  Hi this is 1st line!    
          21
% lfortran_in_main file_19.f90 
 Hi this is 1st line!
1
ERROR STOP
% lfortran file_19.f90       
 Hi this is 1st line!
21

[certik]

I think this is fine, thanks!