ash: move parse-time quote flag detection to run-time

ash: move parse-time quote flag detection to run-time

Because the parser does not recursively parse parameter expansion
with respect to quotes, we can't accurately determine quote status at
parse time.  This patch works around this by moving the quote detection
to run-time where we do interpret it recursively.

Test case:
   foo=\\ echo "<${foo#[\\]}>"
Old result:
   <\>
New result:
   <>

Do not quote back slashes in parameter expansions outside quotes.

Test case:
   a=/b/c/*
   b=\\
   echo ${a%$b*}
Old result:
   /b/c/*
New result:
   /b/c/

Based on commits 880d952, 7cfd8be, 0d7d660 and a7c21a6 from
git://git.kernel.org/pub/scm/utils/dash/dash.git by Herbert Xu

function                                             old     new   delta
argstr                                              1164    1193     +29
memtodest                                            147     174     +27
subevalvar                                          1153    1177     +24
redirect                                            1279    1282      +3
dolatstr                                               5       7      +2
static.spclchars                                      10       9      -1
expandarg                                            962     960      -2
evalcase                                             273     271      -2
evalcommand                                         1204    1197      -7
rmescapes                                            236     227      -9
preglob                                               27       8     -19
evalvar                                              604     582     -22
cmdputs                                              389     334     -55
readtoken1                                          3163    3061    -102
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 5/9 up/down: 85/-219)          Total: -134 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>