hush: implement $'str' bashism

function                                             old     new   delta
parse_dollar_squote                                    -     441    +441
encode_then_expand_vararg                            359     380     +21
parse_stream                                        2252    2271     +19
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 2/0 up/down: 481/0)             Total: 481 bytes

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

shell/hush_test/hush-quoting/dollar_squote_bash1.right

@@ -0,0 +1,10 @@
+a	b
+$'a\tb'
+a
+b c
+def
+a'b c"d e\f
+a3b c3b e33f
+a\80b c08b
+a3b c30b
+x	y

shell/hush_test/hush-quoting/dollar_squote_bash1.tests

@@ -0,0 +1,8 @@
+echo $'a\tb'
+echo "$'a\tb'"
+echo $'a\nb' $'c\nd''ef'
+echo $'a\'b' $'c\"d' $'e\\f'
+echo $'a\63b' $'c\063b' $'e\0633f'
+echo $'a\80b' $'c\608b'
+echo $'a\x33b' $'c\x330b'
+echo $'x\x9y'

shell/hush_test/hush-quoting/dollar_squote_bash2.right

@@ -0,0 +1,6 @@
+strstrstrstrstrstrstrstrstrstrstrstrstrstrstrstrstr
+strstrstrstrstrstrstrstrstrstrstrstrstrstrstrstrstr
+80:\<5C>
+81:\<5C>
+82:\<5C>
+Done:0

shell/hush_test/hush-quoting/dollar_squote_bash2.tests

@@ -0,0 +1,10 @@
+# Embedded NULs
+echo $'str\x00'strstrstrstrstrstrstrstrstrstrstrstrstrstrstrstr
+echo $'str\000'strstrstrstrstrstrstrstrstrstrstrstrstrstrstrstr
+
+# The chars after '\' are hex 0x80,81,82...
+echo 80:$'\<5C>'
+echo 81:$'\<5C>'
+echo 82:$'\<5C>'
+
+echo Done:$?

shell/hush_test/hush-vars/var_bash7.right

@@ -0,0 +1 @@
+B

shell/hush_test/hush-vars/var_bash7.tests

@@ -0,0 +1 @@
+x=AB; echo "${x#$'\x41'}"