bpo-44959: Add fallback to extension modules with '.sl' suffix on HP-UX (GH-27857) (GH-29152)

(cherry picked from commit 2396fa6537d79554ac694dbd2b0b30eeb3476c80)

Co-authored-by: Florin Spătar <florin.spatar@gmail.com>
diff --git a/Python/dynload_hpux.c b/Python/dynload_hpux.c
index e36d608..a533730 100644
--- a/Python/dynload_hpux.c
+++ b/Python/dynload_hpux.c
@@ -13,7 +13,7 @@
 #define FUNCNAME_PATTERN "%.20s_%.200s"
 #endif
 
-const char *_PyImport_DynLoadFiletab[] = {SHLIB_EXT, NULL};
+const char *_PyImport_DynLoadFiletab[] = {SHLIB_EXT, ".sl", NULL};
 
 dl_funcptr _PyImport_FindSharedFuncptr(const char *prefix,
                                        const char *shortname,