build: fix compilation on Windows, and fix EAPI on UNIX

configure.ac

@@ -30,6 +30,8 @@ AM_INIT_AUTOMAKE(1.6 dist-bzip2 dist-xz)
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])])
 AC_CONFIG_HEADERS(config.h)
 AC_GNU_SOURCE
+lt_cv_deplibs_check_method=pass_all
+LT_INIT([win32-dll])
 AC_PROG_LIBTOOL
 AM_PROG_CC_C_O
 ELM_QUICKLAUNCH

src/lib/Enventor.h

@@ -27,6 +27,16 @@ extern "C"
 # else
 #  define EAPI __declspec(dllimport)
 # endif
+#else
+# ifdef __GNUC__
+#  if __GNUC__ >= 4
+#   define EAPI __attribute__ ((visibility("default")))
+#  else
+#   define EAPI
+#  endif
+# else
+#  define EAPI
+# endif
 #endif
 
 /**