[fpc-pascal] Formatting negative zero floating point numbers

[Mark via fpc-pascal]

I have a free pascal and a C program that both generate numeric output in text 
format. I expect both programs to produce the same output and I automatically 
verify that with a simple textual diff in my build process. That works fine in 
general except for negative zero floating point values 
(https://en.wikipedia.org/wiki/Signed_zero). The issue is that FloatToStrF does 
not output a minus sign for those values. Here are short examples to reproduce 
the behavior. The C output is what I would expect.

C:

#include <stdio.h>

int main() {
    double d = -0.0;
    printf("%e\n", d);
    return 0;
}

$ ./main
-0.000000e+00

Pascal (fpc-3.2.2):

program main;

uses
  sysutils;

var
  d :Double;
  s :String;
begin
   d := -0.0;

   Writeln(d);

   WriteStr(s, d);
   Writeln(s);

   Str(d:0:17, s);
   Writeln(s);

   Writeln(FloatToStrF(d, ffExponent, 17, 3));
   Writeln(Format('%e', [d]));
end.

$ ./main
-0.0000000000000000E+000
-0.0000000000000000E+000
-0.00000000000000000
0.0000000000000000E+000
0.0000000000000000E+000


The output of FloatToStrF and Format is different to what I expect and get with 
C. However, it is also different to what Write/WriteStr/Str produces which 
seems inconsistent to me. Is that actually the expected behavior? If yes, is 
there another way to get the desired output? Using WriteStr is no alternative 
for my use case, since I need control over the number of digits for the 
exponent.

Thanks,
Mark
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