new: imap test in gf case

fails on 64bit machines, one of the reasons, why imap.tst fails there
fix: correct results for bigints.tst

99999999...9 is 1*10^something in float, not 1.5...* 10^something
fix: number to float conversion on 64bit machines
Merge pull request #284 from YueRen/thurnau

Thurnau