sh: Fix pathname expansion with quoted slashes like *\/.

These are git commits 36f0fa8fcbc8c7b2b194addd29100fb40e73e4e9 and
d6d06ff5c2ea0fa44becc5ef4340e5f2f15073e4 in dash.

Because this is the first code I'm importing from dash to expand.c, add the
Herbert Xu copyright notice which is in dash's expand.c.

When pathname expanding *\/, the CTLESC representing the quoted state was
erroneously taken as part of the * pathname component. This CTLESC was then
seen by the pattern matching code as escaping the '\0' terminating the
string.

The code is slightly different because dash converts the CTLESC characters
to backslashes and removes all the other CTL* characters to allow
substituting glob(3).

The effect of the bug was also slightly different from dash (where nothing
matched at all). Because a CTLESC can escape a '\0' in some way, whether
files were included despite the bug depended on memory that should not be
read. In particular, on many machines /*\/ expanded to a strict subset of
what /*/ expanded to.

Example:
  echo /*"/null"

This should print /dev/null, not /*/null.

PR:		bin/146378
Obtained from:	dash

1 files changed, 31 insertions, 0 deletions

diff --git a/tools/regression/bin/sh/expansion/pathname2.0 b/tools/regression/bin/sh/expansion/pathname2.0
new file mode 100644
index 0000000..8a884ff
--- /dev/null
+++ b/tools/regression/bin/sh/expansion/pathname2.0
@@ -0,0 +1,31 @@
+# $FreeBSD$
+
+failures=0
+
+check() {
+	testcase=$1
+	expect=$2
+	eval "set -- $testcase"
+	actual="$*"
+	if [ "$actual" != "$expect" ]; then
+		failures=$((failures+1))
+		printf '%s\n' "For $testcase, expected $expect actual $actual"
+	fi
+}
+
+set -e
+T=$(mktemp -d ${TMPDIR:-/tmp}/sh-test.XXXXXX)
+trap 'rm -rf $T' 0
+cd -P $T
+
+mkdir testdir testdir2 'testdir/*' 'testdir/?' testdir/a testdir/b testdir2/b
+mkdir testdir2/.c
+touch testf 'testdir/*/1' 'testdir/?/1' testdir/a/1 testdir/b/1 testdir2/b/.a
+
+check '*\/' 'testdir/ testdir2/'
+check '"testdir/"*"/1"' 'testdir/*/1 testdir/?/1 testdir/a/1 testdir/b/1'
+check '"testdir/"*"/"*' 'testdir/*/1 testdir/?/1 testdir/a/1 testdir/b/1'
+check '"testdir/"*\/*' 'testdir/*/1 testdir/?/1 testdir/a/1 testdir/b/1'
+check '"testdir"*"/"*"/"*' 'testdir/*/1 testdir/?/1 testdir/a/1 testdir/b/1'
+
+exit $((failures != 0))