Win32: suppressed warnings by "-Werror=sign-compare".

src/os/win32/ngx_wsasend_chain.c

diff --git a/src/os/win32/ngx_wsasend_chain.c b/src/os/win32/ngx_wsasend_chain.c
index e28e1ee..fa72524 100644
--- a/src/os/win32/ngx_wsasend_chain.c
+++ b/src/os/win32/ngx_wsasend_chain.c
@@ -34,7 +34,7 @@
 
     /* the maximum limit size is the maximum u_long value - the page size */
 
-    if (limit == 0 || limit > NGX_MAX_UINT32_VALUE - ngx_pagesize) {
+    if (limit == 0 || limit > (off_t) (NGX_MAX_UINT32_VALUE - ngx_pagesize)) {
         limit = NGX_MAX_UINT32_VALUE - ngx_pagesize;
     }
 
@@ -156,7 +156,7 @@
 
         /* the maximum limit size is the maximum u_long value - the page size */
 
-        if (limit == 0 || limit > NGX_MAX_UINT32_VALUE - ngx_pagesize) {
+        if (limit == 0 || limit > (off_t) (NGX_MAX_UINT32_VALUE - ngx_pagesize)) {
             limit = NGX_MAX_UINT32_VALUE - ngx_pagesize;
         }