patch 8.2.0156: various typos in source files and tests

Problem:    Various typos in source files and tests.
Solution:   Fix the typos. (Emir Sari, closes #5532)
diff --git a/src/if_perl.xs b/src/if_perl.xs
index fd9d3d7..12e1a22 100644
--- a/src/if_perl.xs
+++ b/src/if_perl.xs
@@ -930,7 +930,7 @@
 
     if (SvRV(sv) != SvRV(rv))
 	// XXX: This magic variable is a bit confusing...
-	// Is curently refcounted ?
+	// Is currently refcounted ?
 	sv_setsv(sv, rv);
 
     SvREFCNT_dec(rv);