Restore backwards-compatible mappings for 0x5C/0x7E in SJIS (for fast conversion filter)

In d62f535, the legacy mbstring conversion filters for Shift-JIS
was updated to restore backwards-compatible mappings for 0x5C/0x7E.
Make the same change to the newer fast conversion filters.

Author: alexdowad

NEWS

@@ -6,6 +6,10 @@ PHP                                                                        NEWS
   . Fixed bug GH-8655 (Casting an object to array does not unwrap refcount=1
     references). (Nicolas Grekas)
 
+- MBString:
+  . Backwards-compatible mappings for 0x5C/0x7E in Shift-JIS are restored,
+    after they had been changed in 8.1.0. (Alex Dowad)
+
 09 Jun 2022, PHP 8.2.0alpha1
 
 - CLI:

ext/mbstring/libmbfl/filters/mbfilter_sjis.c

@@ -257,11 +257,7 @@ static size_t mb_sjis_to_wchar(unsigned char **in, size_t *in_len, uint32_t *buf
 	while (p < e && out < limit) {
 		unsigned char c = *p++;
 
-		if (c == 0x5C) {
-			*out++ = 0xA5;
-		} else if (c == 0x7E) {
-			*out++ = 0x203E;
-		} else if (c <= 0x7F) {
+		if (c <= 0x7F) {
 			*out++ = c;
 		} else if (c >= 0xA1 && c <= 0xDF) { /* Kana */
 			*out++ = 0xFEC0 + c;
@@ -302,17 +298,7 @@ static void mb_wchar_to_sjis(uint32_t *in, size_t len, mb_convert_buf *buf, bool
 		uint32_t w = *in++;
 		unsigned int s = 0;
 
-		if (w == 0x5C) {
-			/* Unicode 0x5C is a backslash; but Shift-JIS uses 0x5C for the
-			 * Yen sign. JIS X 0208 kuten 0x2140 is a backslash. */
-			s = 0x2140;
-		} else if (w == 0x7E) {
-			/* Unicode 0x7E is a tilde, but Shift-JIS uses 0x7E for overline (or
-			 * macron). JIS X 0208 kuten 0x2141 is 'WAVE DASH' */
-			s = 0x2141;
-		} else if (w == 0xAF || w == 0x203E) { /* U+00AF is MACRON, U+203E is OVERLINE */
-			s = 0x7E; /* Halfwidth overline/macron */
-		} else if (w >= ucs_a1_jis_table_min && w < ucs_a1_jis_table_max) {
+		if (w >= ucs_a1_jis_table_min && w < ucs_a1_jis_table_max) {
 			s = ucs_a1_jis_table[w - ucs_a1_jis_table_min];
 		} else if (w >= ucs_a2_jis_table_min && w < ucs_a2_jis_table_max) {
 			s = ucs_a2_jis_table[w - ucs_a2_jis_table_min];
@@ -324,7 +310,9 @@ static void mb_wchar_to_sjis(uint32_t *in, size_t len, mb_convert_buf *buf, bool
 
 		if (s == 0) {
 			if (w == 0xA5) { /* YEN SIGN */
-				s = 0x5C;
+				s = 0x216F; /* FULLWIDTH YEN SIGN */
+			} else if (w == 0xAF || w == 0x203E) {
+				s = 0x2131; /* FULLWIDTH MACRON */
 			} else if (w == 0xFF3C) { /* FULLWIDTH REVERSE SOLIDUS */
 				s = 0x2140;
 			} else if (w == 0x2225) { /* PARALLEL TO */