mmime: print_header: encode quoted-strings at once

This is maybe a foul compromise between correctness and complexity of
implementation, but it should do the right thing in most cases, and
does not require fully parsing and reconstructing all headers that can
contain phrases.

An 'encoded-word' MUST NOT appear within a 'quoted-string'.  We thus
completely encode the quoted-string (if necessary) as a single
encoded-word, and strip off the quotes.

This should fix encoding of addresses that have both non-ASCII and
special chars such as , and ;.

mmime.c

@@ -317,12 +317,29 @@ print_header(char *line) {
 
 	while (*s) {
 		size_t highbit = 0;
+		int qs = 0;
 		e = s;
 		while (*e && *e == ' ')
 			e++;
-		for (; *e && *e != ' '; e++) {
-			if ((uint8_t)*e >= 127)
-				highbit++;
+
+		if (*e == '"') {  // scan quoted-string, encode at once
+			s = e;
+			for (e++; *e && *e != '"'; e++) {
+				if (*e == '\\')
+					e++;
+				if ((uint8_t)*e >= 127)
+					highbit++;
+			}
+			if (*e == '"')
+				e++;
+			qs = 1;
+		} else {  // scan word
+			while (*e && *e == ' ')
+				e++;
+			for (; *e && *e != ' '; e++) {
+				if ((uint8_t)*e >= 127)
+					highbit++;
+			}
 		}
 
 		if (!highbit) {
@@ -348,6 +365,12 @@ print_header(char *line) {
 force_qp:
 			if (!prevq && *s == ' ')
 				s++;
+
+			if (qs && *s == '"')
+				s++;
+			if (qs && e > s && *(e-1) == '"')
+				e--;
+
 			if (linelen >= 78 - 13 - 4 ||
 			    (e-s < (78 - 13)/3 &&
 			     e-s >= (78 - linelen - 13)/3)) {
@@ -361,6 +384,9 @@ force_qp:
 			printf("?=");
 			linelen += 2;
 			prevq = 1;
+
+			if (qs && *e == '"')
+				e++;
 		}
 		s = e;
 	}