parses a long input numeric string and converts it into a DD number
b = str2dd(a)
string
DD variable
input a DD variable.
--> str2dd('-3.00112233445566778899001122e-7') ans = -3.001122334455667788990011220000E-7 --> str2dd('-1234.000111222333444555666777D22') ans = -1.234000111222333444555666776999E25