Support building with -Werror=strict-prototypes / -Werror=old-style-definition

Unfortunately "-std=c99" is not sufficient to make gcc ignore cold that
uses constructs of earlier C standards, which were abandoned in C99.

See https://lwn.net/ml/fedora-devel/Y1kvF35WozzGBpc8@redhat.com/ for
some related discussion.

Change-Id: I84fd99442d0cc400fa562fa33623c142649230e2
---
M include/osmocom/core/counter.h
M include/osmocom/core/select.h
M include/osmocom/gprs/gprs_bssgp.h
M include/osmocom/gsm/gsm0808.h
M include/osmocom/vty/command.h
M include/osmocom/vty/logging.h
M src/counter.c
M src/gb/gprs_bssgp.c
M src/gsm/gsm0808.c
M src/select.c
M src/time_cc.c
M src/vty/cpu_sched_vty.c
M src/vty/logging_vty.c
M src/vty/stats_vty.c
M tests/abis/abis_test.c
M tests/bitvec/bitvec_test.c
M tests/bsslap/bsslap_test.c
M tests/bssmap_le/bssmap_le_test.c
M tests/codec/codec_ecu_fr_test.c
M tests/ctrl/ctrl_test.c
M tests/fr/fr_test.c
M tests/fsm/fsm_dealloc_test.c
M tests/fsm/fsm_test.c
M tests/gad/gad_test.c
M tests/gb/gprs_bssgp_rim_test.c
M tests/gb/gprs_bssgp_test.c
M tests/gb/gprs_ns_test.c
M tests/gsm0408/gsm0408_test.c
M tests/gsm0502/gsm0502_test.c
M tests/gsm0808/gsm0808_test.c
M tests/gsm23003/gsm23003_test.c
M tests/gsm23236/gsm23236_test.c
M tests/gsm29205/gsm29205_test.c
M tests/gsm48/rest_octets_test.c
M tests/lapd/lapd_test.c
M tests/logging/logging_vty_test.c
M tests/msgb/msgb_test.c
M tests/sms/sms_test.c
M tests/smscb/cbsp_test.c
M tests/sockaddr_str/sockaddr_str_test.c
M tests/socket/socket_test.c
M tests/stats/stats_test.c
M tests/tdef/tdef_test.c
M tests/tdef/tdef_vty_config_root_test.c
M tests/tdef/tdef_vty_config_subnode_test.c
M tests/tdef/tdef_vty_dynamic_test.c
M tests/time_cc/time_cc_test.c
M tests/tlv/tlv_test.c
M tests/use_count/use_count_test.c
M tests/utils/utils_test.c
M tests/vty/vty_test.c
M tests/vty/vty_transcript_test.c
M utils/osmo-aka-verify.c
M utils/osmo-auc-gen.c
M utils/osmo-ns-dummy.c
55 files changed, 214 insertions(+), 214 deletions(-)