Revert "set ENOMEM consistently (I hope everywhere)"

This reverts commit c47dcc40.

This was only set for encoders, but the contract for encoders in
vmod_blobcode.h does not require setting errno, and it isn't
necessary, since insufficient space is the only cause for
encoders to fail (callers don't check errno, and don't need to).

src/hex.c

@@ -84,10 +84,8 @@ hex_encode(const enum encoding enc, char *restrict const buf,
 	assert(enc == HEXUC || enc == HEXLC);
 	if (in == NULL || inlen == 0)
 		return 0;
-	if (buflen < hex_encode_l(inlen)) {
-		errno = ENOMEM;
+	if (buflen < hex_encode_l(inlen))
 		return -1;
-	}
 
 	if (enc != HEXLC)
 		alphabet = hex_alphabet[1];

src/id.c

@@ -55,10 +55,8 @@ id_encode(const enum encoding enc, char *restrict const buf,
 	(void) enc;
 	AN(buf);
 
-	if (buflen < inlen + 1) {
-		errno = ENOMEM;
+	if (buflen < inlen + 1)
 		return -1;
-	}
 	if (in == NULL || inlen == 0)
 		return 0;
 

src/url.c

@@ -95,17 +95,13 @@ url_encode(const enum encoding enc, char *restrict const buf,
 
 	for (int i = 0; i < inlen; i++) {
 		if (isunreserved(in[i])) {
-			if (p == end) {
-				errno = ENOMEM;
+			if (p == end)
 				return -1;
-			}
 			*p++ = in[i];
 		}
 		else {
-			if (p + 3 > end) {
-				errno = ENOMEM;
+			if (p + 3 > end)
 				return -1;
-			}
 			*p++ = '%';
 			*p++ = alphabet[(in[i] & 0xf0) >> 4];
 			*p++ = alphabet[in[i] & 0x0f];