Added a test for the `xz` program path on Cygwin
Fixed the `xz` program path on Cygwin
bug #68 Fixed the `xz` program path on Cygwin (alquerci)

This PR was merged into the 1.1-dev branch.

Discussion
----------

| Q               | A
| --------------- | ---
| Bug fix?        | yes
| New feature?    | no
| BC breaks?      | no
| Deprecations?   | no
| Tests pass?     | yes
| Related tickets | #65
| License         | GNU GPLv3

Commits
-------

7396dca Fixed the `xz` program path on Cygwin
ad0bb6a Added a test for the `xz` program path on Cygwin
Added Makefile GNU coding standards
Replaced from $(commands) to `commands`
Fixed the default value assignment
Fixed unexpected results when word starts with a dash

You should always keep in mind that any builtin or command may support options,
and therefore differ in behavior with arguments starting with a dash. For instance,
even the innocent echo "$word" can give unexpected results when word starts with
a dash.

It is often possible to avoid this problem using echo "x$word", taking the x into
account later in the pipe.
Fixed case don't need to quote the argument; no splitting is performed
Fixed `echo` portability

The simple echo is probably the most surprising source of portability troubles.
It is not possible to use echo portably unless both options and escape sequences
are omitted. Don't expect any option.

Do not use backslashes in the arguments, as there is no consensus on their handling.
For echo `'\n' | wc -l`, the `sh` of Solaris outputs 2, but Bash and Zsh
(in `sh` emulation mode) output 1. The problem is truly `echo`: all the shells
understand `'\n'` as the string composed of a backslash and an `n`. Within a command
substitution, `echo 'string\c'` will mess up the internal state of ksh88 on AIX 6.1
so that it will print the first character `s` only, followed by a newline, and then
entirely drop the output of the next echo in a command substitution.

Because of these problems, do not pass a string containing arbitrary characters to `echo`.
For example, `echo "$foo"` is safe if you know that foo's value cannot contain backslashes
and cannot start with `-`, but otherwise you should use a here-document like this:

    cat <<EOF
    $foo
    EOF
Removed `unset` statement a very old `/bin/sh` that does not support it
Fixed `test` portability

The `-a`, `-o`, `(`, and `)` operands are not portable and should be avoided.
Fixed `expr` portability

When performing arithmetic, use `expr 0 + $var` if `$var` might be a negative
number, to keep expr from interpreting it as an option.

No expr keyword starts with X, so use expr X"word" : 'Xregex' to keep expr from
misinterpreting word.
Added MAKEFLAGS to sub-make invocations

Posix requires make to use MAKEFLAGS to affect the current and recursive
invocations of make, but allows implementations several formats for the variable.
Fixed SHELL variable protection

Posix-compliant make should never acquire the value of `$(SHELL)` from the
environment, even when `make -e` is used.
Fixed sub-make behaviour for export variable
Use -C flag to to call a sub-make to another directory
Removed useless exit call because the `-e` shell flags imply
Replaced from `$(srcdir)/..` to `$(top_srcdir)`
Added CYGPATH_W to convert proper path
Fixed string quoting on the postintall script