libbb: introduce and use strcpy_and_process_escape_sequences

function                                             old     new   delta
strcpy_and_process_escape_sequences                    -      50     +50
bb_process_escape_sequence                           148     138     -10
printf_main                                          789     776     -13
getty_main                                          1897    1831     -66
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/3 up/down: 50/-89)            Total: -39 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/parse_config.c b/libbb/parse_config.c
index 3fff9f2..9dbfaf5 100644
--- a/libbb/parse_config.c
+++ b/libbb/parse_config.c
@@ -187,19 +187,7 @@
 
 #if 0 /* unused so far */
 		if (flags & PARSE_ESCAPE) {
-			const char *from;
-			char *to;
-
-			from = to = tokens[t];
-			while (*from) {
-				if (*from == '\\') {
-					from++;
-					*to++ = bb_process_escape_sequence(&from);
-				} else {
-					*to++ = *from++;
-				}
-			}
-			*to = '\0';
+			strcpy_and_process_escape_sequences(tokens[t], tokens[t]);
 		}
 #endif
 		/* Skip possible delimiters */