do not use std::{to_string,stoi} as they cause problems with cygwin

src/color.cc

@@ -20,7 +20,8 @@ Color str_to_color(const String& color)
     static const Regex rgb_regex{"rgb:[0-9a-fA-F]{6}"};
     if (boost::regex_match(color, rgb_regex))
     {
-        long l = stol(color.substr(ByteCount{4}), NULL, 16);
+        unsigned l;
+        sscanf(color.c_str() + 4, "%x", &l);
         return { (unsigned char)((l >> 16) & 0xFF),
                  (unsigned char)((l >> 8) & 0xFF),
                  (unsigned char)(l & 0xFF) };

src/command_manager.cc

@@ -79,7 +79,7 @@ bool is_horizontal_blank(char c)
 
 struct unterminated_string : parse_error
 {
-    unterminated_string(const std::string& open, const std::string& close, int nest = 0)
+    unterminated_string(const String& open, const String& close, int nest = 0)
         : parse_error{"unterminated string '" + open + "..." + close + "'" +
                       (nest > 0 ? "(nesting: " + to_string(nest) + ")" : "")}
     {}

src/string.cc

@@ -25,14 +25,17 @@ std::vector<String> split(const String& str, char separator)
 
 int str_to_int(const String& str)
 {
-    try
-    {
-        return stoi(str);
-    }
-    catch (std::logic_error&)
-    {
+    int res = 0;
+    if (sscanf(str.c_str(), "%i", &res) != 1)
         throw runtime_error(str + "is not a number");
+    return res;
 }
+
+String to_string(int val)
+{
+    char buf[16];
+    sprintf(buf, "%i", val);
+    return buf;
 }
 
 String option_to_string(const Regex& re)

src/string.hh

@@ -103,10 +103,10 @@ void option_from_string(const String& str, Regex& re);
 
 int str_to_int(const String& str);
 
-using std::to_string;
+String to_string(int val);
 
 template<typename RealType, typename ValueType>
-std::string to_string(const StronglyTypedNumber<RealType, ValueType>& val)
+String to_string(const StronglyTypedNumber<RealType, ValueType>& val)
 {
     return to_string((ValueType)val);
 }