Bugfix/add support curl8

[matheusfillipe]

CHANGES:

1. Continues work from Bugfix/add support curl8 #89 and solves issue with OPT_IPRESOLVE not being defined.
2. Fix codegen.py so that it takes the major version into account.
3. Minor code quality additions to codegen.py
4. Small fixes to examples/multi_and_select.go

Testing

Testing on a mac with libcurl 8.7.1

This now works:

• go run ./examples/misc.go

DEBUG chdir=> (0x1009f8798,0x1400011a420)
init =>0x140001220a0 *curl.CURL
dup =>0x14000122140 *curl.CURL
global init =>(0x0,0x0)
version =>libcurl/8.7.1 (SecureTransport) LibreSSL/3.3.6 zlib/1.2.12 nghttp2/1.63.0
XXXX debug setopt "curl: An unknown option was passed in to libcurl"
set timeout =>(0x0,0x0)
set user_agent =>true
set resolve =>true
set opt!
code -> curl: Couldn't connect to server
================================
pause =>(0x1009f86f8,0x100a87678)
escape =>http%3A%2F%2Fbaidu.com%2F
unescape =>http://baidu.com/--\
unescape lenght =>21
VersionInfo: Age: 10, Version:8.7.1, Host:x86_64-apple-darwin24.0, Features:1366229917, SslVer: (SecureTransport) LibreSSL/3.3.6, LibzV: 1.2.12, ssh:
Protocols:dict, file, ftp, ftps, gopher, gophers, http, https, imap, imaps, ldap, ldaps, mqtt, pop3, pop3s, rtsp, smb, smbs, smtp, smtps, telnet, tftp,
2011-10-02 07:05:58 +0000 UTC
================================
================================

This was erroing to me:

• go run ./examples/multi_and_select.go

# command-line-arguments
examples/multi_and_select.go:33:5: could not determine kind of name for C._FD_SET
cgo:
cc errors for preamble:
examples/multi_and_select.go:9:21: error: expected identifier or '('
    9 | static void _FD_SET(int sysfd, void *set) {
      |                     ^
examples/multi_and_select.go:9:21: error: expected ')'
examples/multi_and_select.go:9:20: note: to match this '('
    9 | static void _FD_SET(int sysfd, void *set) {
      |                 

So I have made some changes to that example and now it works to me (go version go1.23.0 darwin/arm64)

I think some run but don't really test much because they are outdated. Here is the full output for all of them:
examples_output.txt

After Merge

fixes #84

Feedback and help are welcome!