mu4e: use the new command-parser

Update mu4e-proc to use the new mu4e <-> mu protocol

lib/utils/mu-utils.hh

@@ -93,6 +93,17 @@ std::string format (const char *frm, ...) __attribute__((format(printf, 1, 2)));
 std::string format (const char *frm, va_list args) __attribute__((format(printf, 1, 0)));
 
 
+/**
+ * Quote a string -- put in "" and escape any special characters by putting '\'
+ * in front of them.
+ *
+ * @param str
+ *
+ * @return
+ */
+std::string quoted (const std::string& str);
+
+
 /**
  * Convert an ISO date to the corresponding time expressed as a string
  * with a 10-digit time_t