gsm48.h: Make the array extern to a silence a linker warning

/usr/lib/gcc/i686-pc-linux-gnu/4.3.4/../../../../i686-pc-linux-gnu/bin/ld:
Warning: size of symbol `rsl_rlm_cause_strs' changed from 8 in ./openbsc/src/libbsc.a(abis_rsl.o)
to 120 in /usr/local/lib/libosmocore.so

spotted and sent to the list by Andreas
tree: 8c49d3bf6bae6465e44632d43f2a95e19af8f6a0
  1. tests/
  2. .gitignore
  3. configure.in
  4. COPYING
  5. libosmocore.pc.in
  6. Makefile.am