build: fully omit verbose strings and code when disabled

When the compiler supports C99.

- map logging functions to macro stubs when verbose logging is disabled
  and the compiler is C99. Make sure these stubs silence unused variable
  warnings for non-variadic arguments.
  Before this patch they mapped to function stubs, the same codepath
  used for C89 compiler in this configuration.

- introduce new macros to tell the compiler which code to include
  when verbose code is active, or inactive:

  - `CURLVERBOSE`: defined when verbose code is active.
    To enclose blocks of code only used for verbose logging.

  - `VERBOSE(statement);`:
    compile statement when verbose code is active.
    To mark code lines only used for verbose logging.

  - `NOVERBOSE(statement);`:
    compile statement when verbose code is inactive.
    To suppress warnings for arguments passed to logging functions via
    printf masks, e.g. `NOVERBOSE((void)ipaddress);`, yet keeping
    the warning in verbose builds.

  Note these macros are not the same as `CURL_DISABLE_VERBOSE_STRINGS`.
  Verbose code is always active in C89 mode (without variadic macro
  support).

- drop existing uses of `CURL_DISABLE_VERBOSE_STRINGS` where redundant,
  or replace with the above macros. Ending up reducing the number of
  `#ifdef`s, and also the number of lines.

Assisted-by: Daniel Stenberg
Assisted-by: Jay Satiro
Reported-by: Dan Fandrich
Fixes #20341
Refs: #12105 #12167

Closes #20353

.github/workflows/linux.yml

@@ -192,8 +192,9 @@ jobs:
 
           - name: 'openssl arm C89'
             image: ubuntu-24.04-arm
+            install_packages: libssh2-1-dev
             install_steps: pytest
-            configure: CFLAGS=-std=gnu89 --with-openssl --enable-debug --disable-verbose
+            configure: CFLAGS=-std=gnu89 --with-openssl --with-libssh2 --enable-debug --disable-verbose
 
           - name: 'openssl -O3 libssh valgrind 1'
             install_packages: libssh-dev valgrind