hush: improve ${var#...}, ${var:+...} and ${var/.../...} - handle quoting

dollar_altvalue1 test partially fails: word splitting of unquoted ${var:+...}
is not correct

function                                             old     new   delta
encode_then_expand_vararg                              -     443    +443
expand_one_var                                      1599    1610     +11
parse_stream                                        2756    2753      -3
encode_string                                        250     242      -8
setup_heredoc                                        308     298     -10
expand_and_evaluate_arith                            106      96     -10
encode_then_expand_string                            142     126     -16
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/5 up/down: 454/-47)           Total: 407 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/ash_test/ash-quoting/dollar_altvalue1.right

@@ -0,0 +1,16 @@
+Unquoted b c d
+|b|
+|c|
+|d|
+Unquoted 'b c' d
+|b c|
+|d|
+Unquoted "b c" d
+|b c|
+|d|
+Quoted b c d
+|b c d|
+Quoted 'b c' d
+|'b c' d|
+Quoted "b c" d
+|b c d|

shell/ash_test/ash-quoting/dollar_altvalue1.tests

@@ -0,0 +1,16 @@
+f() { for i; do echo "|$i|"; done; }
+x=a
+
+echo Unquoted b c d
+f ${x:+b c d}
+echo Unquoted "'b c' d"
+f ${x:+'b c' d}
+echo Unquoted '"b c" d'
+f ${x:+"b c" d}
+
+echo Quoted b c d
+f "${x:+b c d}"
+echo Quoted "'b c' d"
+f "${x:+'b c' d}"
+echo Quoted '"b c" d'
+f "${x:+"b c" d}"

shell/ash_test/ash-quoting/dollar_repl_bash1.right

@@ -0,0 +1,14 @@
+|y|
+|zx|
+|y|
+|zx|
+|y zx|
+|y zx|
+|y|
+|zy|
+|z|
+|y|
+|zy|
+|z|
+|y zy z|
+|y zy z|

shell/ash_test/ash-quoting/dollar_repl_bash1.tests

@@ -0,0 +1,12 @@
+f() { for i; do echo "|$i|"; done; }
+v=xx
+
+f ${v/'x'/"y z"}
+f ${v/"x"/'y z'}
+f "${v/'x'/"y z"}"
+f "${v/"x"/'y z'}"
+
+f ${v//'x'/"y z"}
+f ${v//"x"/'y z'}
+f "${v//'x'/"y z"}"
+f "${v//"x"/'y z'}"

shell/ash_test/ash-quoting/squote_in_varexp.right

@@ -1,5 +1,9 @@
 z
 z
+z
+z
+y
+y
 y
 y
 Ok:0

shell/ash_test/ash-quoting/squote_in_varexp.tests

@@ -1,6 +1,10 @@
 x=yz
 echo ${x#'y'}
 echo "${x#'y'}"
+echo ${x#"y"}
+echo "${x#"y"}"
 echo ${x%'z'}
 echo "${x%'z'}"
+echo ${x%"z"}
+echo "${x%"z"}"
 echo Ok:$?

shell/ash_test/ash-quoting/squote_in_varexp2.right

@@ -1,3 +1,5 @@
 Nothing:
 Nothing:
+Nothing:
+Nothing:
 Ok:0

shell/ash_test/ash-quoting/squote_in_varexp2.tests

@@ -1,4 +1,6 @@
 x='\\\\'
 printf Nothing:'%s\n' ${x#'\\\\'}
 printf Nothing:'%s\n' "${x#'\\\\'}"
+printf Nothing:'%s\n' ${x#"\\\\\\\\"}
+printf Nothing:'%s\n' "${x#"\\\\\\\\"}"
 echo Ok:$?

shell/ash_test/ash-z_slow/many_ifs.tests

@@ -229,8 +229,8 @@ do
 						'')	split "$d0$f1$d1$f2$d2$f3$d3" "[2]($f1)($f2)" "($f1)($f2)" ;;
 						' ')	;;
 						*)	x=$f2$d2$f3$d3
-							x=${x# } #was x=${x#' '} hush needs fixing for this to work
-							x=${x% } #was x=${x%' '}
+							x=${x#' '}
+							x=${x%' '}
 							split "$d0$f1$d1$f2$d2$f3$d3" "[3]($f1)($f2)($f3)" "($f1)($x)"
 							;;
 						esac