fixed: Big::ToString method

in some cases when in the output string the exponent should be equal zero
       the method changes the exponent to one so the last digit from the mantissa
       was lost
 
       sample:
       Big<1,1> a;
       a.info = 0;
       a.mantissa = 2147483649u; // (bin) 10000000000000000000000000000001
       // first and last bit in the mantissa is set
       a.exponent = 0;
       std::cout << a << std::endl;

       priovious result: 2147483640
       it was treated as 214748364e+1

       also the method has been a little improved




git-svn-id: svn://ttmath.org/publicrep/ttmath/trunk@312 e52654a7-88a9-db11-a3e9-0013d4bc506e

CHANGELOG

@@ -4,6 +4,10 @@ Version 0.9.2 prerelease (2010.09.19):
                when the argument was negative (they only returned 2)
     * fixed:   recurrence calling in Big::FromString(const std::string &, uint, const wchar_t **, bool *)
                it should have the signature: Big::FromString(const std::string &, uint, const char **, bool *)               
+    * fixed:   Big::ToString method
+               in some cases when in the output string the exponent should be equal zero
+               the method changes the exponent to one so the last digit from the mantissa
+               was lost
     * added:   some missing operators
                UInt::operator~()    /* bitwise neg  */
                UInt::operator&()    /* bitwise and  */