configure: check for strtoull on msvc

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: James Almer <jamrial@gmail.com>
(cherry picked from commit b52d3574)

Changelog

@@ -2,6 +2,7 @@ Entries are sorted chronologically from oldest to youngest within each release,
 releases are sorted from youngest to oldest.
 
 version 3.1.6:
+- configure: check for strtoull on msvc
 - http: move chunk handling from http_read_stream() to http_buf_read().
 - http: make length/offset-related variables unsigned.
 - ffserver: Check chunk size

configure

@@ -6197,6 +6197,7 @@ __declspec($_restrict) void* foo(int);
 EOF
     fi
     check_func strtoll || add_cflags -Dstrtoll=_strtoi64
+    check_func strtoull || add_cflags -Dstrtoull=_strtoui64
 fi
 
 for pfx in "" host_; do