perl: update to 5.26.1

Required changes:

* Add qualifying '.' to scripts or to @INC, as appropriate since we're
  enabling default_inc_excludes_dot;

* Add new platform/library definitions like double-double format and
  locale library functions/headers;

* Delete patch 020 as it's been upstreamed;

Optional changes:

* Instead of using -@rm and having that fail, emit an error message,
  and be ignored, just use @rm -f instead which will always succeed.

Security
[CVE-2017-12837] Heap buffer overflow in regular expression compiler

Compiling certain regular expression patterns with the case-insensitive
modifier could cause a heap buffer overflow and crash perl. This has
now been fixed. [perl #131582]

[CVE-2017-12883] Buffer over-read in regular expression parser

For certain types of syntax error in a regular expression pattern, the
error message could either contain the contents of a random, possibly
large, chunk of memory, or could crash perl. This has now been fixed.
[perl #131598]

[CVE-2017-12814] $ENV{$key} stack buffer overflow on Windows

A possible stack buffer overflow in the %ENV code on Windows has been
fixed by removing the buffer completely since it was superfluous anyway.
[perl #131665]

Signed-off-by: Philip Prindeville <philipp@redfish-solutions.com>

lang/perl/files/version.config

@@ -1,11 +1,11 @@
 # Set the version here
 PERL_REVISION=5
-PERL_VERSION=24
+PERL_VERSION=26
 PERL_SUBVERSION=1
 
 # (api_revison, api_version, api_subversion) = (revision, version, 0) usually
 PERL_API_REVISION=5
-PERL_API_VERSION=24
+PERL_API_VERSION=26
 PERL_API_SUBVERSION=0
 
 known_extensions='B Compress/Raw/Zlib Cwd DB_File Data/Dumper Devel/DProf Devel/PPPort Devel/Peek Digest/MD5 Digest/SHA Encode Fcntl File/Glob Filter/Util/Call GDBM_File Hash/Util I18N/Langinfo IO IPC/SysV List/Util MIME/Base64 Math/BigInt/FastCalc NDBM_File ODBM_File Opcode POSIX PerlIO/encoding PerlIO/scalar PerlIO/via SDBM_File Socket Storable Sys/Hostname Sys/Syslog Text/Soundex Time/HiRes Time/Piece Unicode/Normalize Win32 Win32API/File Win32CORE XS/APItest XS/Typemap attrs re threads threads/shared Hash/Util/FieldHash'