problem to find some C functions

```bash
/afs/ifh.de/group/pitz/doocs/develop/kalantar/dev/root_with_helpers/.extras/root/misc/memstat/src/TMemStatHook.cxx: In static member function ‘static void* (* TMemStatHook::GetMallocHook())(size_t, const void*)’:
/afs/ifh.de/group/pitz/doocs/develop/kalantar/dev/root_with_helpers/.extras/root/misc/memstat/src/TMemStatHook.cxx:51:11: error: ‘__malloc_hook’ was not declared in this scope
return __malloc_hook;
^
/afs/ifh.de/group/pitz/doocs/develop/kalantar/dev/root_with_helpers/.extras/root/misc/memstat/src/TMemStatHook.cxx: In static member function ‘static void (* TMemStatHook::GetFreeHook())(void*, const void*)’:
/afs/ifh.de/group/pitz/doocs/develop/kalantar/dev/root_with_helpers/.extras/root/misc/memstat/src/TMemStatHook.cxx:64:11: error: ‘__free_hook’ was not declared in this scope
return __free_hook;
^
/afs/ifh.de/group/pitz/doocs/develop/kalantar/dev/root_with_helpers/.extras/root/misc/memstat/src/TMemStatHook.cxx: In static member function ‘static void TMemStatHook::SetMallocHook(TMemStatHook::MallocHookFunc_t)’:
/afs/ifh.de/group/pitz/doocs/develop/kalantar/dev/root_with_helpers/.extras/root/misc/memstat/src/TMemStatHook.cxx:77:4: error: ‘__malloc_hook’ was not declared in this scope
__malloc_hook = p;
^
/afs/ifh.de/group/pitz/doocs/develop/kalantar/dev/root_with_helpers/.extras/root/misc/memstat/src/TMemStatHook.cxx: In static member function ‘static void TMemStatHook::SetFreeHook(TMemStatHook::FreeHookFunc_t)’:
/afs/ifh.de/group/pitz/doocs/develop/kalantar/dev/root_with_helpers/.extras/root/misc/memstat/src/TMemStatHook.cxx:88:4: error: ‘__free_hook’ was not declared in this scope
__free_hook = p;
^
/afs/ifh.de/group/pitz/doocs/develop/kalantar/dev/root_with_helpers/.extras/root/misc/memstat/src/TMemStatHook.cxx: In static member function ‘static void* (* TMemStatHook::GetMallocHook())(size_t, const void*)’:
/afs/ifh.de/group/pitz/doocs/develop/kalantar/dev/root_with_helpers/.extras/root/misc/memstat/src/TMemStatHook.cxx:55:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^
/afs/ifh.de/group/pitz/doocs/develop/kalantar/dev/root_with_helpers/.extras/root/misc/memstat/src/TMemStatHook.cxx: In static member function ‘static void (* TMemStatHook::GetFreeHook())(void*, const void*)’:
/afs/ifh.de/group/pitz/doocs/develop/kalantar/dev/root_with_helpers/.extras/root/misc/memstat/src/TMemStatHook.cxx:68:1: warning: control reaches end of non-void function [-Wreturn-type]
}
^
gmake[2]: *** [misc/memstat/CMakeFiles/MemStat.dir/build.make:163: misc/memstat/CMakeFiles/MemStat.dir/src/TMemStatHook.cxx.o] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:16563: misc/memstat/CMakeFiles/MemStat.dir/all] Error 2
gmake: *** [Makefile:156: all] Error 2
```