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
% reverting to rev 0
reverting foo
M foo
diff --git a/foo b/foo
old mode 100755
new mode 100644