Move definition of php_le_stream_context

From ext/standard/file.h to main/streams/php_stream_context.h
This reduces some dependency of main/ on ext/standard

Author: Girgias

ext/standard/file.h

@@ -36,7 +36,6 @@ PHPAPI PHP_FUNCTION(fpassthru);
 
 PHP_MINIT_FUNCTION(user_streams);
 
-PHPAPI int php_le_stream_context(void);
 PHPAPI zend_result php_copy_file(const char *src, const char *dest);
 PHPAPI zend_result php_copy_file_ex(const char *src, const char *dest, int src_flags);
 PHPAPI zend_result php_copy_file_ctx(const char *src, const char *dest, int src_flags, php_stream_context *ctx);

main/streams/php_stream_context.h

@@ -53,6 +53,7 @@ struct _php_stream_context {
 };
 
 BEGIN_EXTERN_C()
+PHPAPI int php_le_stream_context(void);
 PHPAPI void php_stream_context_free(php_stream_context *context);
 PHPAPI php_stream_context *php_stream_context_alloc(void);
 PHPAPI zval *php_stream_context_get_option(php_stream_context *context,