Ensure module initialisation is exported globally

The generated module initialisation function fails to export because of
the "-fvisibility-hidden" resulting in an import failure on missing
symbol. Alter the visibility of the initialisation function to "default"
to ensure that it winds up as "global" in the module binary.

Signed-off-by: aneejit1 <aneejit1@gmail.com>

sipgen/gencode.c

@@ -2324,14 +2324,21 @@ static void generateModInitStart(moduleDef *mod, int gen_c, FILE *fp)
 "#define SIP_MODULE_RETURN(r)    return\n"
 "#endif\n"
 "\n"
+"#if (defined(__GNUC__) && __GNUC__ >= 4) || defined(__clang__)\n"
+"#pragma GCC visibility push(default)\n"
+"#endif\n"
 "#if defined(SIP_STATIC_MODULE)\n"
 "%sSIP_MODULE_TYPE SIP_MODULE_ENTRY()\n"
 "#else\n"
 "PyMODINIT_FUNC SIP_MODULE_ENTRY()\n"
 "#endif\n"
 "{\n"
+"#if (defined(__GNUC__) && __GNUC__ >= 4) || defined(__clang__)\n"
+"#pragma GCC visibility pop\n"
+"#endif\n"
         , mod->name
         , mod->name
+        , (gen_c ? "" : "extern \"C\" ")
         , (gen_c ? "" : "extern \"C\" "));
 }