bug#12832: 24.3.50; Emacs lockup when idle

[Andy Moreton <andrewjmoreton@gmail.com>]

Windows Emacs (built from r110828) was idle for a few minutes while I made a
coffee. On returning, emacs was completely unresponsive and redisplay
was not drawing anything.

Windows XP SP3
MinGW gcc 4.7.2

Backtrace from "thread apply all bt full":

Thread 6 (Thread 8744.0x2080):
#0  0x7c90120f in ntdll!DbgUiConnectToDbg () from C:\WINDOWS\system32\ntdll.dll
No symbol table info available.
#1  0x7c952119 in ntdll!KiIntSystemCall () from C:\WINDOWS\system32\ntdll.dll
No symbol table info available.
#2  0x00000005 in ?? ()
No symbol table info available.
#3  0x00000004 in ?? ()
No symbol table info available.
#4  0x00000001 in ?? ()
No symbol table info available.
#5  0x5ad3ffd0 in ?? ()
No symbol table info available.
#6  0x00000000 in ?? ()
No symbol table info available.

Lisp Backtrace:
"redisplay_internal (C function)" (0x167235c)

Thread 5 (Thread 8744.0x5ec):
#0  0x7c90e514 in ntdll!LdrAccessResource () from C:\WINDOWS\system32\ntdll.dll
No symbol table info available.
#1  0x7c90d9da in ntdll!ZwReadFile () from C:\WINDOWS\system32\ntdll.dll
No symbol table info available.
#2  0x7c801879 in ReadFile () from C:\WINDOWS\system32\kernel32.dll
No symbol table info available.
#3  0x00000610 in ?? ()
No symbol table info available.
#4  0x00000000 in ?? ()
No symbol table info available.

Lisp Backtrace:
"redisplay_internal (C function)" (0x167235c)

Thread 4 (Thread 8744.0x241c):
#0  0x7c90e514 in ntdll!LdrAccessResource () from C:\WINDOWS\system32\ntdll.dll
No symbol table info available.
#1  0x7c90df5a in ntdll!ZwWaitForSingleObject () from 
C:\WINDOWS\system32\ntdll.dll
No symbol table info available.
#2  0x7c8025db in WaitForSingleObjectEx () from C:\WINDOWS\system32\kernel32.dll
No symbol table info available.
#3  0x000005d0 in ?? ()
No symbol table info available.
#4  0x00000000 in ?? ()
No symbol table info available.

Lisp Backtrace:
"redisplay_internal (C function)" (0x167235c)

Thread 3 (Thread 8744.0x21d4):
#0  0x7c90e514 in ntdll!LdrAccessResource () from C:\WINDOWS\system32\ntdll.dll
No symbol table info available.
#1  0x7e4191be in USER32!GetProcessWindowStation () from 
C:\WINDOWS\system32\user32.dll
No symbol table info available.
#2  0x7e4191f1 in USER32!GetMessageW () from C:\WINDOWS\system32\user32.dll
No symbol table info available.
#3  0x0114875d in w32_msg_pump (msg_buf=0x5b5aff54) at w32fns.c:2386
         msg = {
           hwnd = 0x3f9500bc,
           message = 0xf,
           wParam = 0x0,
           lParam = 0x0,
           time = 0x6cc97f02,
           pt = {
             x = 0xdd,
             y = 0x2f
           }
         }
         result = 0x0
         focus_window = 0x403
#4  0x0114899b in w32_msg_worker@4 (arg=0x0) at w32fns.c:2612
         msg = {
           hwnd = 0x86af0b20,
           message = 0x80502fc0,
           wParam = 0x0,
           lParam = 0x0,
           time = 0x0,
           pt = {
             x = 0x80502fc8,
             y = 0x8dedcca0
           }
         }
         dummy_buf = {
           next = 0x0,
           w32msg = {
             msg = {
               hwnd = 0x0,
               message = 0x0,
               wParam = 0x0,
               lParam = 0x0,
               time = 0x0,
               pt = {
                 x = 0x0,
                 y = 0x0
               }
             },
             dwModifiers = 0x0,
             rect = {
               left = 0x0,
               top = 0x0,
               right = 0x0,
               bottom = 0x0
             }
           },
           result = 0x0,
           completed = 0x0
         }
#5  0x7c80b729 in KERNEL32!GetModuleFileNameA () from 
C:\WINDOWS\system32\kernel32.dll
No symbol table info available.
#6  0x00000000 in ?? ()
No symbol table info available.

Lisp Backtrace:
"redisplay_internal (C function)" (0x167235c)

Thread 2 (Thread 8744.0x1840):
#0  0x7c90e514 in ntdll!LdrAccessResource () from C:\WINDOWS\system32\ntdll.dll
No symbol table info available.
#1  0x7c90d21a in ntdll!ZwDelayExecution () from C:\WINDOWS\system32\ntdll.dll
No symbol table info available.
#2  0x7c8023f1 in SleepEx () from C:\WINDOWS\system32\kernel32.dll
No symbol table info available.
#3  0x00000000 in ?? ()
No symbol table info available.

Lisp Backtrace:
"redisplay_internal (C function)" (0x167235c)

Thread 1 (Thread 8744.0xf50):
#0  0x7c90e514 in ntdll!LdrAccessResource () from C:\WINDOWS\system32\ntdll.dll
No symbol table info available.
#1  0x7c90d2aa in ntdll!ZwDuplicateObject () from C:\WINDOWS\system32\ntdll.dll
No symbol table info available.
#2  0x7c80df03 in KERNEL32!DuplicateHandle () from 
C:\WINDOWS\system32\kernel32.dll
No symbol table info available.
#3  0xffffffff in ?? ()
No symbol table info available.
#4  0xfffffffe in ?? ()
No symbol table info available.
#5  0xffffffff in ?? ()
No symbol table info available.
#6  0x0162acb8 in real_itimer ()
No symbol table info available.
#7  0x00000000 in ?? ()
No symbol table info available.

Lisp Backtrace:
"redisplay_internal (C function)" (0x167235c)