Parser parses "-i" as 0+0i at beginning of string

[DKLoehr]

If an equation or variable string expression starts with "-i", the parser evaluates that part as being 0. The result should be 0+-1i, but for some reason this results in 0+0i instead.
Workaround is to replace it with -1i, which is parsed correctly.

[DKLoehr]

Automated the above workaround, so the substring "-i" is now automatically replaced with "-1i"