Fix clang compiler warnings on FreeBSD in erts

The following are deliberately left, as I have only a list of compiler
warnings and no system to test on:
hipe/hipe_x86_signal.c:264:5: warning: no previous prototype for function '_sigaction' [-Wmissing-prototypes]
int __SIGACTION(int signum, const struct sigaction *act, struct sigaction *oldact)
    ^
hipe/hipe_x86_signal.c:222:21: note: expanded from macro '__SIGACTION'
                    ^
1 warning generated.
sys/unix/sys_float.c:835:16: warning: declaration of 'struct exception' will not be visible outside of this function [-Wvisibility]
matherr(struct exception *exc)
               ^
sys/unix/sys_float.c:835:1: warning: no previous prototype for function 'matherr' [-Wmissing-prototypes]
matherr(struct exception *exc)
^
2 warnings generated.
drivers/unix/unix_efile.c:1504:11: warning: implicit declaration of function 'sendfile' [-Wimplicit-function-declaration]
        retval = sendfile(in_fd, out_fd, *offset, SENDFILE_CHUNK_SIZE,
                 ^
1 warning generated.

1 files changed, 0 insertions, 8 deletions

diff --git a/erts/etc/common/erlexec.c b/erts/etc/common/erlexec.c
index d865164bb0..60d7c4ce02 100644
--- a/erts/etc/common/erlexec.c
+++ b/erts/etc/common/erlexec.c
@@ -184,7 +184,6 @@ void error(char* format, ...);
 #if !defined(ERTS_HAVE_SMP_EMU)
 static void usage_notsup(const char *switchname);
 #endif
-static void usage_msg(const char *msg);
 static char **build_args_from_env(char *env_var);
 static char **build_args_from_string(char *env_var);
 static void initial_argv_massage(int *argc, char ***argv);
@@ -1132,13 +1131,6 @@ usage_notsup(const char *switchname)
 #endif
 
 static void
-usage_msg(const char *msg)
-{
-    fprintf(stderr, "%s\n", msg);
-    usage_aux();
-}
-
-static void
 usage_format(char *format, ...)
 {
     va_list args;