fix several problems with config parser:

 a bug where it underflows the string
 a bug where it never frees parser_t struct
make read_config() return 0 if parser is NULL,
 make config_close() accept and ignore NULL parser -
 eliminates many if() blocks
reverse the sense of parser bit flags - negative flags
 are harder to grok.
hexdump: revert the change to use config parser, it is BIGGER
 and also requires additional quirks in parser
*: explicitly use PARSER_NORMAL instead of 0

function                                             old     new   delta
login_main                                          1575    1596     +21
config_close                                          18      29     +11
bbunpack                                             383     391      +8
qgravechar                                           106     109      +3
rtnl_tab_initialize                                  121     117      -4
expand                                              1697    1693      -4
man_main                                             717     712      -5
nameif_main                                          674     668      -6
hexdump_main                                         597     591      -6
read_config                                          217     209      -8
dnsd_main                                           1478    1470      -8
sysctl_main                                          203     189     -14
config_open2                                          44      25     -19
make_device                                         1177    1141     -36
config_read                                          597     549     -48
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/11 up/down: 43/-158)         Total: -115 bytes

1 files changed, 2 insertions, 2 deletions

diff --git a/init/init.c b/init/init.c
index 884603af3..e02773cc0 100644
--- a/init/init.c
+++ b/init/init.c
@@ -701,13 +701,13 @@ static void parse_inittab(void)
 		new_init_action(ASKFIRST, bb_default_login_shell, VC_4);
 		/* sysinit */
 		new_init_action(SYSINIT, INIT_SCRIPT, "");
-
 		return;
 	}
 	/* optional_tty:ignored_runlevel:action:command
 	 * Delims are not to be collapsed and need exactly 4 tokens
 	 */
-	while (config_read(parser, token, 4, 0, "#:", PARSE_DONT_TRIM|PARSE_DONT_REDUCE|PARSE_LAST_IS_GREEDY)) {
+	while (config_read(parser, token, 4, 0, "#:",
+				PARSE_NORMAL & ~(PARSE_TRIM | PARSE_COLLAPSE))) {
 		int action;
 		char *tty = token[0];