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, 12 insertions, 4 deletions

diff --git a/util-linux/hexdump.c b/util-linux/hexdump.c
index 8ac12f082..48edd70a9 100644
--- a/util-linux/hexdump.c
+++ b/util-linux/hexdump.c
@@ -16,11 +16,19 @@
 
 static void bb_dump_addfile(dumper_t *dumper, char *name)
 {
-	parser_t *parser = config_open2(name, xfopen_for_read);
-	while (config_read(parser, &name, 1, 1, "# \t", 0)) {
-		bb_dump_add(dumper, name);
+	char *p;
+	FILE *fp;
+	char *buf;
+
+	fp = xfopen_for_read(name);
+	while ((buf = xmalloc_fgetline(fp)) != NULL) {
+		p = skip_whitespace(buf);
+		if (*p && (*p != '#')) {
+			bb_dump_add(dumper, p);
+		}
+		free(buf);
 	}
-	config_close(parser);
+	fclose(fp);
 }
 
 static const char *const add_strings[] = {