Allow static linkage with libsctp.a

[georgthegreat]

At the time libsctp.a does not provide sctp_connectx symbol which is forward-declared in its interface.

This PR suggests renaming sctp_connectx3 to sctp_connectx to workaround this.

We don't use pull requests anymore. Please follow Linux netdev community patch
posting standard instead. Post your patches to linux-sctp@vger.kernel.org and
they will be very welcomed. Thanks!

[marceloleitner]

If I hack the tests Makefile.am with this:

--- a/src/func_tests/Makefile.am
+++ b/src/func_tests/Makefile.am
@@ -8,7 +8,7 @@ AM_CPPFLAGS = -I. -I$(top_builddir)/src/include -I$(top_srcdir)/src/testlib \
               -g -O2 -fno-strict-aliasing -Wall -Wstrict-prototypes \
               -Wimplicit-function-declaration

-AM_LDFLAGS = -lpthread
+AM_LDFLAGS = -lpthread -static

It works without your patch and fails with it, with this error:

  CCLD     test_connectx
/usr/bin/ld: ../../src/lib/.libs/libsctp.a(connectx.o): in function `__connectx':
/home/mrl/eng/lksctp-tools/src/lib/connectx.c:98: multiple definition of `sctp_connectx'; ../../src/lib/.libs/libsctp.a(connectx.o):/home/mrl/eng/lksctp-tools/src/lib/connectx.c:146: first defined here
collect2: error: ld returned 1 exit status
make: *** [Makefile:1015: test_connectx] Erro 1

What am I missing? How did you test this?

[georgthegreat]

Well, it looks like there is no way (meaning that I know no way) to combine all off

1. Static linkage
2. Dynamic linkage
3. Versioned symbols

One should either pick (1) + (2) or (2) + (3).