Currently the build of v4-2-test is broken on fedora 22:

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[1786/4218] Compiling source4/lib/http/http.c
../source4/lib/http/http.c: In function ‘http_parse_headers’:
../source4/lib/http/http.c:115:19: error: format ‘%a’ expects argument of type ‘float *’, but argument 3 has type ‘char **’ [-Werror=format=]
  n = sscanf(line, "%a[^:]: %a[^\r\n]\r\n", &key, &value);
                   ^
../source4/lib/http/http.c:115:19: error: format ‘%a’ expects argument of type ‘float *’, but argument 4 has type ‘char **’ [-Werror=format=]
../source4/lib/http/http.c: In function ‘http_parse_response_line’:
../source4/lib/http/http.c:161:19: error: format ‘%a’ expects argument of type ‘float *’, but argument 3 has type ‘char **’ [-Werror=format=]
  n = sscanf(line, "%a[^/]/%c.%c %d %a[^\r\n]\r\n",
                   ^
../source4/lib/http/http.c:161:19: error: format ‘%a’ expects argument of type ‘float *’, but argument 7 has type ‘char **’ [-Werror=format=]
cc1: some warnings being treated as errors
Waf: Leaving directory `/data/obnox/devel/samba/4.2/v4-2-test/bin'
Build failed:  -> task failed (err #1): 
        {task: cc http.c -> http_1.o}
Makefile:8: recipe for target 'all' failed
make: *** [all] Error 1

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