tests: Windows compatibility fixes
- printenv.py, md5sum.py, simplemerge, test-archive, test-merge1,
test-merge-symlinks: set standard streams to binary mode
- test-encode: replace "gunzip" by "gzip -d"
- test-hup: requires fifo
% qimport non-existing-file
abort: unable to read non-existing-file
% build diff with CRLF
adding b
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
% qimport CRLF diff
adding b.diff to series file
applying b.diff
Now at: b.diff