Fix xlc17 clang 15 warnings in security and servicability

Compiling on AIX with xlc17 which contains the new clang 15 frontend shows the following warnings:

src/java.security.jgss/share/native/libj2gss/NativeUtil.h:30:
src/java.security.jgss/share/native/libj2gss/gssapi.h:48:5: error: 'TARGET_OS_MAC' is not defined, evaluates to 0 [-Werror,-Wundef]
#if TARGET_OS_MAC && (defined(ppc) || defined(ppc64) || defined(i386) || defined(x86_64))
^

src/jdk.jdwp.agent/share/native/libdt_socket/socketTransport.c:718:33: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
struct in6_addr mappedAny = IN6ADDR_ANY_INIT;
^~~~~~~~~~~~~~~~
/usr/include/netinet/in.h:454:32: note: expanded from macro 'IN6ADDR_ANY_INIT'
#define IN6ADDR_ANY_INIT {0, 0, 0, 0}