tests: don't rely on 'false' exit code in test-run-tests.t On Solaris: $ sh -c 'false ; echo $?' 255

tests: don't use alias alias doesn't work in Solaris sh.

tests: don't include plain 'diff -U0' content in test-diff-unified.t The only purpose of 'diff -U0' was to show that 'hg diff -U0' did almost the same. Unfortunately 'diff -U0' on Solaris gives incorrect line numbers. Masking it with globs wouldn't it make sense, so removing it is the best solution.