The pygobject property helper erroneously disallows negative float or double values because of a mistake in the type checking.

Steps to reproduce:
>>> import gobject
>>> gobject.property(type=float,minimum=-1)
Traceback (most recent call last):

+ Trace 216300

Expected behavior:
Negative minimum values should be allowed for float and double.

The range checking for float values in gobject.propertyhelper.property._get_minimum is incorrect, the minimum float value is not G_MINFLOAT, it is -G_MAXFLOAT. G_MINFLOAT is zero. Likewise for G_DOUBLE which is the translated value for python float.

The workaround is, obviously, to use __gproperties__ instead of the property helper.