hush: fix globbing+backslashes in unquoted $var expansion

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>

shell/hush_test/hush-glob/glob2.right

@@ -0,0 +1,18 @@
+Expected Actual
+Z\*    : Z\*
+Z*     : Z*
+Z\f    : Z\f
+Z\*    : Z\*
+
+Z\z    : Z\z
+Zz     : Zz
+Z\z    : Z\z
+Z\z    : Z\z
+
+Z\     : Z\
+Z\     : Z\
+
+Z\f Zf : Z\f Zf
+Z\f Zf : Z\f Zf
+
+Done: 0

shell/hush_test/hush-glob/glob2.tests

@@ -0,0 +1,27 @@
+# This test demonstrates that in unquoted $v, backslashes expand by this rule:
+# \z -> \\\z; \<eol> -> \\<eol> (for any z, special or not),
+# and subsequently globbing converts \\ to \ and treats \z as literal z
+# even if it is a special char.
+
+>'Zf'
+>'Z\f'
+	echo 'Expected' 'Actual'
+v='\*'; echo 'Z\*    :' Z$v
+        echo 'Z*     :' Z\*
+        echo 'Z\f    :' Z\\*
+        echo 'Z\*    :' Z\\\*  # NB! only this matches Z$v output
+echo
+v='\z'; echo 'Z\z    :' Z$v
+        echo 'Zz     :' Z\z
+        echo 'Z\z    :' Z\\z
+        echo 'Z\z    :' Z\\\z
+echo
+v='\';  echo 'Z\     :' Z$v
+        echo 'Z\     :' Z\\
+echo
+v='*';  echo 'Z\f Zf :' Z$v
+        echo 'Z\f Zf :' Z*
+echo
+
+rm 'Z\f' 'Zf'
+echo Done: $?