tool_doswin: Improve sanitization processing

- Add unit test 1604 to test the sanitize_file_name function.

- Use -DCURL_STATICLIB when building libcurltool for unit testing.

- Better detection of reserved DOS device names.

- New flags to modify sanitize behavior:

SANITIZE_ALLOW_COLONS: Allow colons
SANITIZE_ALLOW_PATH: Allow path separators and colons
SANITIZE_ALLOW_RESERVED: Allow reserved device names
SANITIZE_ALLOW_TRUNCATE: Allow truncating a long filename

- Restore sanitization of banned characters from user-specified outfile.

Prior to this commit sanitization of a user-specified outfile was
temporarily disabled in 2b6dadc because there was no way to allow path
separators and colons through while replacing other banned characters.
Now in such a case we call the sanitize function with
SANITIZE_ALLOW_PATH which allows path separators and colons to pass
through.


Closes https://github.com/curl/curl/issues/624
Reported-by: Octavio Schroeder

tests/data/test1604

@@ -0,0 +1,25 @@
+<testcase>
+<info>
+<keywords>
+unittest
+</keywords>
+</info>
+
+#
+# Client-side
+<client>
+<server>
+none
+</server>
+<features>
+unittest
+</features>
+ <name>
+Test WIN32/MSDOS filename sanitization
+ </name>
+<tool>
+unit1604
+</tool>
+</client>
+
+</testcase>