vi: use basic regular expressions for search

Both traditional vi and vim use basic regular expressions for
search.  Also, they don't allow matches to extend across line
endings.  Thus with the file:

   123
   234

the search '/2.*4$' should find the second '2', not the first.

Make BusyBox vi do the same.

Whether or not VI_REGEX_SEARCH is enabled:

function                                             old     new   delta
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0)                 Total: 0 bytes
Signed-off-by: NAndrey Dobrovolsky <andrey.dobrovolsky.odessa@gmail.com>
Signed-off-by: NRon Yorston <rmy@pobox.com>
Signed-off-by: NDenys Vlasenko <vda.linux@googlemail.com>

editors/vi.c

@@ -2378,9 +2378,9 @@ static char *char_search(char *p, const char *pat, int dir_and_range)
 	char *q;
 	int i, size, range, start;
 
-	re_syntax_options = RE_SYNTAX_POSIX_EXTENDED;
+	re_syntax_options = RE_SYNTAX_POSIX_BASIC & (~RE_DOT_NEWLINE);
 	if (ignorecase)
-		re_syntax_options = RE_SYNTAX_POSIX_EXTENDED | RE_ICASE;
+		re_syntax_options |= RE_ICASE;
 
 	memset(&preg, 0, sizeof(preg));
 	err = re_compile_pattern(pat, strlen(pat), &preg);