libbpf: start v1.6 development cycle

With libbpf v1.5.0 release out, start v1.6 dev cycle.

Signed-off-by: Andrii Nakryiko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/lib/bpf/libbpf.map

···
 		ring__consume_n;
 		ring_buffer__consume_n;
 } LIBBPF_1.4.0;
+
+LIBBPF_1.6.0 {
+} LIBBPF_1.5.0;

tools/lib/bpf/libbpf_version.h

···
 #define __LIBBPF_VERSION_H
 
 #define LIBBPF_MAJOR_VERSION 1
-#define LIBBPF_MINOR_VERSION 5
+#define LIBBPF_MINOR_VERSION 6
 
 #endif /* __LIBBPF_VERSION_H */