Fix of escape_strings_cstyle(), which did not enclose a single word

string containing semicolon ';' character into quotes.

src/libslic3r/Config.cpp

@@ -73,7 +73,7 @@ std::string escape_strings_cstyle(const std::vector<std::string> &strs)
         bool should_quote = strs.size() == 1 && str.empty();
         for (size_t i = 0; i < str.size(); ++ i) {
             char c = str[i];
-            if (c == ' ' || c == '\t' || c == '\\' || c == '"' || c == '\r' || c == '\n') {
+            if (c == ' ' || c == ';' || c == '\t' || c == '\\' || c == '"' || c == '\r' || c == '\n') {
                 should_quote = true;
                 break;
             }