autofs-5.1.8 - fix missing include in hash.h

From: Sam James <sam@gentoo.org>

Fixes a build failure with the musl libc:
```
../include/hash.h:74:8: error: unknown type name '__always_inline'
   74 | static __always_inline uint32_t hash_64(uint64_t val, unsigned int bits)
      |        ^~~~~~~~~~~~~~~
```

We need to include stddef.h from linux-headers to ensure _always_inline
is always defined.

Bug: https://bugs.gentoo.org/828918
Tested-by: Yixun Lan <dlan@gentoo.org>
Signed-off-by: Sam James <sam@gentoo.org>
---
 CHANGELOG      |    1 +
 include/hash.h |    1 +
 2 files changed, 2 insertions(+)

diff --git a/CHANGELOG b/CHANGELOG
index dd76b02f..53b487eb 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -18,6 +18,7 @@
 - fix handling of incorrect return from umount_ent().
 - dont use initgroups() at spawn.
 - fix bashism in configure.
+- musl: fix missing include in hash.h.
 
 19/10/2021 autofs-5.1.8
 - add xdr_exports().
diff --git a/include/hash.h b/include/hash.h
index 2447f293..010acd7e 100644
--- a/include/hash.h
+++ b/include/hash.h
@@ -3,6 +3,7 @@
 /* Fast hashing routine for ints,  longs and pointers.
    (C) 2002 Nadia Yvette Chambers, IBM */
 
+#include <linux/stddef.h>
 #include <sys/types.h>
 #include <stdint.h>