[core][android][darwin] Move number format to i18n

include/mbgl/i18n/number_format.hpp

@@ -0,0 +1,15 @@
+#pragma once
+
+#include <string>
+
+namespace mbgl {
+namespace platform {
+
+std::string formatNumber(double number,
+                         const std::string& localeId,
+                         const std::string& currency,
+                         uint8_t minFractionDigits,
+                         uint8_t maxFractionDigits);
+
+} // namespace platform
+} // namespace mbgl

include/mbgl/util/platform.hpp

@@ -16,9 +16,6 @@ std::string lowercase(const std::string &string);
 // Gets the name of the current thread.
 std::string getCurrentThreadName();
 
-std::string formatNumber(double number, const std::string& localeId, const std::string& currency,
-                         uint8_t minFractionDigits, uint8_t maxFractionDigits);
-
 // Set the name of the current thread, truncated at 15.
 void setCurrentThreadName(const std::string& name);