netperf: add instruction on how to build netperf for osv

tools/netperf/netperf.txt

+To measure netwroking throughput we use netperf-2.6.0,
+
+The netperf client isn't working in OS-v, only netserver,
+and only after applying a small patch to the source.
+
+
+How to compile netperf from source so it'll run on osv:
+
+1. checkout the netperf-2.6.0 source from the following URL:
+http://www.netperf.org/netperf/DownloadNetperf.html
+
+2. compile regularly on linux, we're building the binaries that run on the host now.
+$ ./configure
+$ make
+$ sudo make install
+
+3. apply the osv patch to netperf
+$ patch -p1 < osv.patch
+
+4. build again
+$ make clean
+$ make CFLGAS="-fPIC -shared"
+
+5. copy src/netserver and use it in OS-v.
+
+
+
+Starting netserver
+
+[osv]$ run /tools/netserver-osv -D -4 -f
+
+ 
+Connecting using netperf
+
+[linux]$ ./netperf-linux -H 192.168.122.100
+
+

tools/netperf/osv.patch

+diff --git a/src/netlib.c b/src/netlib.c
+index 206e002..8433d59 100644
+--- a/src/netlib.c
++++ b/src/netlib.c
+@@ -888,7 +888,7 @@ void
+ stop_timer()
+ {
+ #ifndef WIN32
+-  alarm(0);
++  //alarm(0);
+ #else
+   /* at some point we may need some win32 equivalent */
+   if (hAlarm != (HANDLE) INVALID_HANDLE_VALUE) {
+@@ -1095,6 +1095,7 @@ void
+ start_timer(int time)
+ {
+ 
++    return;
+ #ifdef WIN32
+   /*+*+SAF What if StartTimer is called twice without the first timer */
+   /*+*+SAF expiring? */