[MEDIUM] moved stats and buffer generic functions to new files

Neither the primitives used to write data to a buffer, nor the stats
dump functions are HTTP-specific anymore. Move them to dedicated
files
diff --git a/Makefile.osx b/Makefile.osx
index a1a6c47..a92e857 100644
--- a/Makefile.osx
+++ b/Makefile.osx
@@ -100,6 +100,7 @@
        src/time.o src/fd.o src/regex.o src/cfgparse.o src/server.o \
        src/checks.o src/queue.o src/client.o src/proxy.o src/proto_uxst.o \
        src/proto_http.o src/stream_sock.o src/appsession.o src/backend.o \
+       src/senddata.o src/dumpstats.o \
        src/session.o src/hdr_idx.o src/ev_select.o src/ev_poll.o src/acl.o \
        src/memory.o