hush: more rodust detection of unterminated strings etc;

fix a case where we forget to copy `cmd` text;
 optimize nommu heredoc helper by not passing environment to it;
 add several tests

function                                             old     new   delta
add_till_closing_paren                               256     308     +52
parse_stream                                        2337    2378     +41
add_till_backquote                                    82     111     +29
re_execute_shell                                     269     284     +15
handle_dollar                                        802     812     +10
parse_stream_dquoted                                 316     320      +4
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 6/0 up/down: 151/0)             Total: 151 bytes

shell/hush_test/hush-misc/heredoc_huge.right

@@ -0,0 +1,3 @@
+546ed3f5c81c780d3ab86ada14824237  -
+546ed3f5c81c780d3ab86ada14824237  -
+End

shell/hush_test/hush-misc/heredoc_huge.tests

@@ -0,0 +1,9 @@
+# This creates 120k heredoc
+echo 'cat <<HERE | md5sum' >"$0.tmp"
+yes "123456789 123456789 123456789 123456789" | head -3000 >>"$0.tmp"
+echo 'HERE' >>"$0.tmp"
+
+yes "123456789 123456789 123456789 123456789" | head -3000 | md5sum
+. "$0.tmp"
+rm "$0.tmp"
+echo End

shell/hush_test/hush-psubst/tick_huge.right

@@ -0,0 +1,3 @@
+546ed3f5c81c780d3ab86ada14824237  -
+546ed3f5c81c780d3ab86ada14824237  -
+End

shell/hush_test/hush-psubst/tick_huge.tests

@@ -0,0 +1,7 @@
+# This creates 120k file
+yes "123456789 123456789 123456789 123456789" | head -3000 >>"$0.tmp"
+
+echo "`cat $0.tmp`" | md5sum
+rm "$0.tmp"
+yes "123456789 123456789 123456789 123456789" | head -3000 | md5sum
+echo End

shell/hush_test/hush-z_slow/leak_all2.right

@@ -0,0 +1,3 @@
+Warm up
+Measuring memory leak...
+Ok

shell/hush_test/hush-z_slow/leak_all2.tests

@@ -0,0 +1,87 @@
+# "Check many leaks" test #2
+# Cramming all kinds of weird commands in here.
+# As you find leaks, please create separate, small test
+# for each leak.
+# Narrowing down the leak using this large test may be difficult.
+# It is intended to be a blanket "is everything ok?" test
+
+echo "Warm up"
+local_var="local val"
+export dev_null="/dev/null"
+>$dev_null
+echo hi1 $local_var `echo ho` >>/dev/null
+echo hi2 $local_var </dev/null | echo 2>&- | cat 1<>/dev/null
+{ echo hi4 $local_var `echo ho` 1<>/dev/null; }
+( echo hi4 $local_var `echo ho` 1<>/dev/null )
+if echo $local_var; false
+    then echo not run
+    elif false <$dev_null
+    then none
+    else cat 0<>$dev_null 1<>"$dev_null"
+fi >>/dev/null
+{
+    if echo $local_var; then cat <<HERE
+Hi cat
+HERE
+    fi >>/dev/null
+} 1<>/dev/null
+while { echo $dev_null >>$dev_null; }; do cat <"$dev_null"; break; done
+( until { echo $dev_null >>$dev_null | false; }; do cat <"$dev_null"; break; done ) <$dev_null
+
+memleak
+
+echo "Measuring memory leak..."
+# Please copy the entire block from above verbatim
+local_var="local val"
+export dev_null="/dev/null"
+>$dev_null
+echo hi1 $local_var `echo ho` >>/dev/null
+echo hi2 $local_var </dev/null | echo 2>&- | cat 1<>/dev/null
+{ echo hi4 $local_var `echo ho` 1<>/dev/null; }
+( echo hi4 $local_var `echo ho` 1<>/dev/null )
+if echo $local_var; false
+    then echo not run
+    elif false <$dev_null
+    then none
+    else cat 0<>$dev_null 1<>"$dev_null"
+fi >>/dev/null
+{
+    if echo $local_var; then cat <<HERE
+Hi cat
+HERE
+    fi >>/dev/null
+} 1<>/dev/null
+while { echo $dev_null >>$dev_null; }; do cat <"$dev_null"; break; done
+( until { echo $dev_null >>$dev_null | false; }; do cat <"$dev_null"; break; done ) <$dev_null
+
+# And same again
+
+local_var="local val"
+export dev_null="/dev/null"
+>$dev_null
+echo hi1 $local_var `echo ho` >>/dev/null
+echo hi2 $local_var </dev/null | echo 2>&- | cat 1<>/dev/null
+{ echo hi4 $local_var `echo ho` 1<>/dev/null; }
+( echo hi4 $local_var `echo ho` 1<>/dev/null )
+if echo $local_var; false
+    then echo not run
+    elif false <$dev_null
+    then none
+    else cat 0<>$dev_null 1<>"$dev_null"
+fi >>/dev/null
+{
+    if echo $local_var; then cat <<HERE
+Hi cat
+HERE
+    fi >>/dev/null
+} 1<>/dev/null
+while { echo $dev_null >>$dev_null; }; do cat <"$dev_null"; break; done
+( until { echo $dev_null >>$dev_null | false; }; do cat <"$dev_null"; break; done ) <$dev_null
+
+memleak
+kb=$?
+if test $kb -le 4; then
+    echo Ok #$kb
+else
+    echo "Bad: $kb kb (or more) leaked"
+fi