x509asn1: fixed and adapted for ASN1tostr unit testing

- move defines to header file
- make bit2str require < 8 unused bits
- make bool strings stricter
- make UTime2str show + or - for custom time zones
- removed unused 'type' argument to ASN1tostr() function
- fix int2str for negative values. All values below 10000 are now shown
  in decimal properly, also possibly negative values.

Add unit test 1667 to verify ASN1tostr

Closes #21013

tests/data/Makefile.am

@@ -222,7 +222,7 @@ test1640 test1641 test1642 test1643 \
 \
 test1650 test1651 test1652 test1653 test1654 test1655 test1656 test1657 \
 test1658 test1659 test1660 test1661 test1662 test1663 test1664 test1665 \
-test1666 \
+test1666 test1667 \
 \
 test1670 test1671 \
 \

tests/data/test1667

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="US-ASCII"?>
+<testcase>
+<info>
+<keywords>
+unittest
+ASN1tostr
+x509asn1
+</keywords>
+</info>
+
+# Client-side
+<client>
+<features>
+unittest
+</features>
+<name>
+ASN1tostr unit tests
+</name>
+</client>
+</testcase>