libtasn1: Import libtasn1-4.19.0

Import a very trimmed-down set of libtasn1 files:

  curl -L -O https://ftp.gnu.org/gnu/libtasn1/libtasn1-4.19.0.tar.gz
  tar xvzf libtasn1-4.19.0.tar.gz
  rm -rf grub-core/lib/libtasn1
  mkdir -p grub-core/lib/libtasn1/lib
  mkdir -p grub-core/lib/libtasn1/tests
  cp libtasn1-4.19.0/{README.md,COPYING} grub-core/lib/libtasn1
  cp libtasn1-4.19.0/lib/{coding.c,decoding.c,element.c,element.h,errors.c,gstr.c,gstr.h,int.h,parser_aux.c,parser_aux.h,structure.c,structure.h} grub-core/libtasn1/lib
  cp libtasn1-4.19.0/lib/includes/libtasn1.h grub-core/lib/libtasn1
  cp libtasn1-4.19.0/tests/{CVE-2018-1000654-1_asn1_tab.h,CVE-2018-1000654-2_asn1_tab.h,CVE-2018-1000654.c,object-id-decoding.c,object-id-encoding.c,octet-string.c,reproducers.c,Test_overflow.c,Test_simple.c,Test_strings.c} grub-core/lib/libtasn1/tests
  rm -rf libtasn1-4.19.0*

Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Stefan Berger <stefanb@linux.ibm.com>

grub-core/lib/libtasn1/COPYING

@@ -0,0 +1,16 @@
+LICENSING
+=========
+
+The libtasn1 library is released under the GNU Lesser General Public
+License (LGPL) version 2.1 or later; see [COPYING.LESSER](doc/COPYING.LESSER)
+for the license terms.
+
+The GNU LGPL applies to the main libtasn1 library, while the
+included applications library are under the GNU GPL version 3.
+The libtasn1 library is located in the lib directory, while the applications
+in src/.
+
+The documentation in doc/ is under the GNU FDL license 1.3.
+
+For any copyright year range specified as YYYY-ZZZZ in this package
+note that the range specifies every single year in that closed interval.