tidy-up: miscellaneous

- examples: sync debug output printf masks.
- INSTALL-CMAKE.md: tidy up section for some options.
- curl_sha512_256: delete comment suggesting an optimization.
- vtls/keylog: scope a variable.
- vtls/openssl: make a source code URL a permalink.
- vtls/schannel: drop redundant parentheses.
- test1119.pl: robustify `$1` -> `$s`.
- sync arg names in comments to match the code.
- tidy up and minor fixes to comments.
- fix formatting/indenting/comment/newline/include nits.
- move `UNITTEST` protos next to definitions, sync their argument names.
- make variables static.
- add parentheses to Perl `open()` calls.
- drop unnecessary double quotes in Perl.
- clang-format.

Closes #21000

.github/workflows/linux.yml

@@ -309,7 +309,8 @@ jobs:
               -Wl,-rpath,/home/runner/rustls/lib
               -Wl,-rpath,/home/linuxbrew/.linuxbrew/opt/gsasl/lib
 
-            PKG_CONFIG_PATH: "/home/runner/wolfssl-opensslextra/lib/pkgconfig:\
+            PKG_CONFIG_PATH: "\
+              /home/runner/wolfssl-opensslextra/lib/pkgconfig:\
               /home/runner/mbedtls/lib/pkgconfig:\
               /home/runner/rustls/lib/pkgconfig:\
               /home/linuxbrew/.linuxbrew/opt/gsasl/lib/pkgconfig"
@@ -330,7 +331,8 @@ jobs:
               -Wl,-rpath,/home/linuxbrew/.linuxbrew/opt/libnghttp3/lib
               -Wl,-rpath,/home/linuxbrew/.linuxbrew/opt/c-ares/lib
 
-            PKG_CONFIG_PATH: "/home/linuxbrew/.linuxbrew/opt/libngtcp2/lib/pkgconfig:\
+            PKG_CONFIG_PATH: "\
+              /home/linuxbrew/.linuxbrew/opt/libngtcp2/lib/pkgconfig:\
               /home/linuxbrew/.linuxbrew/opt/libnghttp3/lib/pkgconfig:\
               /home/linuxbrew/.linuxbrew/opt/c-ares/lib/pkgconfig"
             generate: >-
@@ -354,7 +356,8 @@ jobs:
             CC: clang-20
             CFLAGS: -fsanitize=address,undefined,signed-integer-overflow -fno-sanitize-recover=undefined,integer -Wformat -Werror=format-security -Werror=array-bounds -g
             LDFLAGS: -fsanitize=address,undefined -fno-sanitize-recover=undefined,integer -ldl -lubsan -Wl,-rpath,/home/linuxbrew/.linuxbrew/opt/c-ares/lib
-            PKG_CONFIG_PATH: "/home/linuxbrew/.linuxbrew/opt/libssh2/lib/pkgconfig:\
+            PKG_CONFIG_PATH: "\
+              /home/linuxbrew/.linuxbrew/opt/libssh2/lib/pkgconfig:\
               /home/linuxbrew/.linuxbrew/opt/libngtcp2/lib/pkgconfig:\
               /home/linuxbrew/.linuxbrew/opt/libnghttp3/lib/pkgconfig:\
               /home/linuxbrew/.linuxbrew/opt/c-ares/lib/pkgconfig"