patch 8.2.3967: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more errors to errors.h.
diff --git a/src/if_mzsch.c b/src/if_mzsch.c
index 41b6d00..2d87238 100644
--- a/src/if_mzsch.c
+++ b/src/if_mzsch.c
@@ -668,14 +668,14 @@
     if (!hMzGC)
     {
 	if (verbose)
-	    semsg(_(e_loadlib), gc_dll, GetWin32Error());
+	    semsg(_(e_could_not_load_library_str_str), gc_dll, GetWin32Error());
 	return FAIL;
     }
 
     if (!hMzSch)
     {
 	if (verbose)
-	    semsg(_(e_loadlib), sch_dll, GetWin32Error());
+	    semsg(_(e_could_not_load_library_str_str), sch_dll, GetWin32Error());
 	return FAIL;
     }
 
@@ -689,7 +689,7 @@
 	    FreeLibrary(hMzGC);
 	    hMzGC = 0;
 	    if (verbose)
-		semsg(_(e_loadfunc), thunk->name);
+		semsg(_(e_could_not_load_library_function_str), thunk->name);
 	    return FAIL;
 	}
     }
@@ -703,7 +703,7 @@
 	    FreeLibrary(hMzGC);
 	    hMzGC = 0;
 	    if (verbose)
-		semsg(_(e_loadfunc), thunk->name);
+		semsg(_(e_could_not_load_library_function_str), thunk->name);
 	    return FAIL;
 	}
     }