Fix submitted.
1) Removed _USE_32BIT_TIME_T from code base.
2) Added a macro to replace timegm() with _mkgmtime() on VC8+ (supports 32 and 64 bit time_t)
Simple test performed on VC 7.1/8 and 9 (VS 2003/05/08)
C:\gnu\exiv2\msvc\bin\Release>exiv2 -a 1:00:00 ad \R.tiff && exiv2 -pt \R.tiff | grep DateTimeOriginal
Exif.Photo.DateTimeOriginal Ascii 20 2009:04:26 10:38:18
C:\gnu\exiv2\msvc\bin\Release>exiv2 -a 1:00:00 ad \R.tiff && exiv2 -pt \R.tiff | grep -i time
Exif.Image.DateTimeOriginal Ascii 20 2009:04:26 11:38:18
C:\gnu\exiv2\msvc\bin\Release>
3) Cosmetic fix to basicio.cpp
Fixed nasty little <tab> I missed when I committed basicio.cpp on Sunday (apologies)