To avoid hitting `-Wreserved-macro-identifier` where possible.
- amigaos: introduce local macro instead of reusing `__request()`.
- easy_lock: avoid redefining `__has_builtin()`.
Follow-up to 33fd57b8ff#9062
- rand: drop interim macro `_random()`.
- windows: rename local macro `_tcsdup()` to `Curl_tcsdup()`.
To avoid using the reserved macro namespace and to avoid
colliding with `_tcsdup()` as defined by Windows headers.
- checksrc: ban `_tcsdup()` in favor of `Curl_tcsdup()`.
- tool_doswin: avoid redefining `_use_lfn()` (MS-DOS).
- tool_findfile: limit `__NO_NET_API` hack to AmigaOS.
Syncing this pattern with `lib/netrc.c`.
Follow-up to 784a8ec2c1#16279
- examples/http2-upload: avoid reserved namespace for local macro.
More cases will be removed when dropping WinCE support via #17927.
Cases remain when defining external macros out of curl's control.
Ref: #18477Closes#18482
ad26a6cb99