test1521: test *all* curl_easy_setopt options

mk-lib1521.pl generates a test program (lib1521.c) that calls
curl_easy_setopt() for every known option with a few typical values to
make sure they work (ignoring the return codes).

Some small changes were necessary to avoid asserts and NULL accesses
when doing this.

The perl script needs to be manually rerun when we add new options.

Closes #1543

tests/data/Makefile.inc

@@ -160,7 +160,7 @@ test1500 test1501 test1502 test1503 test1504 test1505 test1506 test1507 \
 test1508 test1509 test1510 test1511 test1512 test1513 test1514 test1515 \
 test1516 test1517 \
 \
-test1520 \
+test1520 test1521 \
 \
 test1525 test1526 test1527 test1528 test1529 test1530 test1531 test1532 \
 test1533 test1534 test1535 test1536 test1537 test1538 \

tests/data/test1521

@@ -0,0 +1,30 @@
+<testcase>
+<info>
+<keywords>
+curl_easy_setopt
+</keywords>
+</info>
+
+#
+# Client-side
+<client>
+<server>
+none
+</server>
+<tool>
+lib1521
+</tool>
+
+ <name>
+try ALL curl_easy_setopt options
+ </name>
+ <command>
+unused
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+</verify>
+</testcase>