docs: add CURLOPT type change history, drop casts where present

Some CURLOPT constants defined in the curl public headers were initially
enums (= ints), or macros with bare numeric values. Recent curl releases
upgraded them to `long` constants, to make them pass correctly to
`curl_easy_setop()` by default, i.e. without requiring a `(long)` cast.

This patch drops such casts from the examples embedded in the docs. At
the same time it documents which curl release made them `long` types,
to keep them useful when working with previous libcurl versions.

Also:
- drop a `(long)` cast that was never necessary.
- CURLOPT_ALTSVC_CTRL.md: bump local copy of macros to long.
- test1119: make it ignore symbols ending with an underscore, to skip
  wildcard, e.g. `**CURLAUTH_***`.

Closes #18130

docs/libcurl/opts/CURLOPT_NETRC_FILE.md

@@ -60,6 +60,11 @@ int main(void)
 }
 ~~~
 
+# HISTORY
+
+**CURL_NETRC_*** enums became `long` types in 8.13.0, prior to this version
+a `long` cast was necessary when passed to curl_easy_setopt(3).
+
 # %AVAILABILITY%
 
 # RETURN VALUE