Better kernel module checking (#1032)

* Better kernel module checking

* fix linting

* better error messages

* fix linting

* fix linting again

* Change Semigroups -> semigroups

PackageInfo.g

@@ -375,7 +375,7 @@ PackageDoc := rec(
 ),
 
 Dependencies := rec(
-  GAP := ">=4.12.0",
+  GAP := ">=4.12.1",
   NeededOtherPackages := [["datastructures", ">=0.2.5"],
                           ["digraphs", ">=1.6.2"],
                           ["genss", ">=1.6.5"],
@@ -406,13 +406,10 @@ BannerString := Concatenation(
   "------\n"),
 
 AvailabilityTest := function()
-  local semigroups_so;
-  semigroups_so := Filename(DirectoriesPackagePrograms("semigroups"),
-                            "semigroups.so");
-  if (not "semigroups" in SHOW_STAT()) and semigroups_so = fail then
+  if not IsKernelExtensionAvailable("semigroups") then
     LogPackageLoadingMessage(PACKAGE_WARNING,
-                             "the kernel module is not compiled, ",
-                             "the package cannot be loaded.");
+                             ["the kernel module is not compiled, ",
+                              "the package cannot be loaded."]);
     return fail;
   fi;
   return true;

init.g

@@ -13,15 +13,9 @@ if not IsBound(ORBC) then
   BindGlobal("HTValue_TreeHash_C", fail);
 fi;
 
-# the kernel module makes use of the c functions HTAdd_TreeHash_C and
-# HTValue_TreeHash_C and so we should only use the part of the kernel module
-# using these functions if Orb is compiled.
-_SEMIGROUPS_SO := Filename(DirectoriesPackagePrograms("semigroups"),
-                           "semigroups.so");
-if _SEMIGROUPS_SO <> fail then
-  LoadDynamicModule(_SEMIGROUPS_SO);
+if LoadKernelExtension("semigroups") = false then
+    Error("failed to load Semigroups kernel extension");
 fi;
-Unbind(_SEMIGROUPS_SO);
 
 if not IsBound(UserHomeExpand) then
   BindGlobal("UserHomeExpand", USER_HOME_EXPAND);