Improve error: incorrect scientific notation

[helins]

A double specified in incorrect scientific notation results in an empty message:

12e

12e12.78

;; READER: Reader error: Parse error at Position{line=1, column=6} Source: <.> Message: null

[mikera]

Might be fixed by replacement Reader

[helins]

Both now throw :UNDECLADED: 12e -> "e" is undeclared ; 12e12.78 -> ".78 is undeclared".

Better but ideally it would fail at the level of the reader.