Usage of atof() to parse floats in trader language was locale-dependent:
if locale specified something other than dot as decimal separator,
parsing floats (which are always dot-separated in queries) failed.
Replaced atof() with simple sufficient custom parser.

Added a unit test.


FIXED-IN: 4.7.1
(cherry picked from commit d522bb4d44bfe53d19b2072ccbabd24151b70a75)