Correct typos as per GH 20435

In GH 20435 many typos in our C code were corrected.  However, this pull
request was not applied to blead and developed merge conflicts.  I
extracted diffs for the individual modified files and applied them with
'git apply', excepting four files where patch conflicts were reported.
Those files were:

        handy.h
        locale.c
        regcomp.c
        toke.c

We can handle these in a subsequent commit. Also, had to run these two
programs to keep 'make test_porting' happy:

        $ ./perl -Ilib regen/uconfig_h.pl
        $ ./perl -Ilib regen/regcomp.pl regnodes.h

1 files changed, 1 insertions, 1 deletions

diff --git a/perlapi.h b/perlapi.h
index 0d66a68371..d93ee199b7 100644
--- a/perlapi.h
+++ b/perlapi.h
@@ -13,7 +13,7 @@
 /*
  * This file used to declare accessor functions for Perl variables
  * when PERL_GLOBAL_STRUCT was enabled, but that no longer exists.
- * This file is kept for backwards compatiblity with XS code that
+ * This file is kept for backwards compatibility with XS code that
  * might include it.
  */
 #ifndef __perlapi_h__