misc: Fix compiler warnings about the static_assert macro with gcc 4.8

The modified macro is still working on a gcc 4.7 and gcc 4.8 after the
removal of the typedef and addition of the unused attribute.

include/osmocom/core/msgb.h: In function ‘msgb_alloc_headroom’:
include/osmocom/core/utils.h:40:51: warning: typedef ‘dummyheadroom_bigger’ locally defined but not used [-Wunused-local-typedefs]
 #define osmo_static_assert(exp, name) typedef int dummy##name [(exp) ? 1 : -1];
                                                   ^
include/osmocom/core/msgb.h:386:2: note: in expansion of macro ‘osmo_static_assert’
  osmo_static_assert(size > headroom, headroom_bigger);
  ^

0 files changed, 0 insertions, 0 deletions