begin_code.h (DECLSPEC): remove a leftover definition as dllexport
for non-WIN32 cases, which used to break compilations with gcc-3.x.

diff -r 08f3b56969b1 include/begin_code.h
--- a/include/begin_code.h	Mon Sep 08 01:36:22 2014 -0400
+++ b/include/begin_code.h	Mon Sep 08 13:23:14 2014 +0300
@@ -64,8 +64,7 @@
 # else
 #  if defined(__GNUC__) && __GNUC__ >= 4
 #   define DECLSPEC __attribute__ ((visibility("default")))
-#  elif defined(__GNUC__) && __GNUC__ >= 2
-#   define DECLSPEC __declspec(dllexport)
+/* FIXME: some distros have visibility attributes backported to gcc3.4 */
 #  else
 #   define DECLSPEC
 #  endif