Gambit doesn't display integer part of numbers

whose absolute value is 0 < x < 1.

I adjusted the code of 'compose-with-digits' for such case.

Also, I updated tests and added test-Gambit.scm and test-Guile.scm.

I confirmed that all tests are passed.

OS: Windows 8.1 (64bit)

DevTool: MSYS2/MinGW-w64 (64bit) (gcc version 7.1.0 (Rev2, Built by MSYS2 project))

Scheme: Gauche v0.9.6_pre4, Sagittarius v0.8.4, Racket v6.7

        Gambit v4.8.8, Guile v2.0.14