clang/LLVM for Windows (clang-cl) conformance errors

[walbourn]

Trying to build this library using clang/LLVM for Windows 15.0.1 fails with the following fatal errors due to conformance:

First, the code assumes it's safe to convert a const char[] array to a void*. It would work as const void*.

D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\zre_msg.c(1932,5): error: no matching function for call to 'zlist_append'
    zlist_append (hello_groups, "Name: Brutus");
    ^~~~~~~~~~~~
D:\vcpkg\installed\x64-clangcl-dynamic\include/zlist.h(74,5): note: candidate function not viable: no known conversion from 'const char[13]' to 'void *' for 2nd argument
    zlist_append (zlist_t *self, void *item);
    ^
D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\zre_msg.c(1933,5): error: no matching function for call to 'zlist_append'
    zlist_append (hello_groups, "Age: 43");
    ^~~~~~~~~~~~
D:\vcpkg\installed\x64-clangcl-dynamic\include/zlist.h(74,5): note: candidate function not viable: no known conversion from 'const char[8]' to 'void *' for 2nd argument
    zlist_append (zlist_t *self, void *item);
    ^
D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\zre_msg.c(1938,5): error: no matching function for call to 'zhash_insert'
    zhash_insert (hello_headers, "Name", "Brutus");
    ^~~~~~~~~~~~
D:\vcpkg\installed\x64-clangcl-dynamic\include/zhash.h(48,5): note: candidate function not viable: no known conversion from 'const char[7]' to 'void *' for 3rd argument
    zhash_insert (zhash_t *self, const char *key, void *item);
    ^
D:\vcpkg\installed\x64-clangcl-dynamic\include/zactor.h(34,5): note: candidate function not viable: no known conversion from 'const char[4]' to 'void *' for 2nd argument
    zactor_new (zactor_fn task, void *args);

Second, it doesn't respect that string literals are read-only:

D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\perf_local.c(128,36): warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
            if (s_node_recv (node, "WHISPER", "R:WHISPER"))
                                   ^
D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\perf_local.c(128,47): warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
            if (s_node_recv (node, "WHISPER", "R:WHISPER"))
                                              ^
D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\perf_local.c(133,32): warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
        if (s_node_recv (node, "WHISPER", "R:WHISPER"))
                               ^
D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\perf_local.c(133,43): warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
        if (s_node_recv (node, "WHISPER", "R:WHISPER"))
                                          ^
D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\perf_local.c(150,36): warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
            if (s_node_recv (node, "SHOUT", "R:SHOUT"))
                                   ^
D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\perf_local.c(150,45): warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
            if (s_node_recv (node, "SHOUT", "R:SHOUT"))
                                            ^
D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\perf_local.c(155,32): warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
        if (s_node_recv (node, "SHOUT", "R:SHOUT"))
                               ^
D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\perf_local.c(155,41): warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
        if (s_node_recv (node, "SHOUT", "R:SHOUT"))
                                        ^
[7/25] D:\vcpkg\installed\x64-clangcl-dynamic\tools\llvm\clang-cl.exe   -TP  -ID:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src -ID:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\include -ID:\vcpkg\buildtrees\zyre\x64-clangcl-dynamic-dbg -imsvcD:\vcpkg\installed\x64-clangcl-dynamic\include /nologo /DWIN32 /D_WINDOWS /W3 /utf-8 /GR /EHsc  -m64 /D_DEBUG /MDd /Z7 /Ob0 /Od /RTC1 /showIncludes /FoCMakeFiles\perf_remote.dir\src\perf_remote.c.obj /FdCMakeFiles\perf_remote.dir\ -c -- D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\perf_remote.c
D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\perf_remote.c(49,30): warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
            sending_cookie = "R:HELLO";
                             ^
D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\perf_remote.c(63,34): warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
                sending_cookie = "R:WHISPER";
                                 ^
D:\vcpkg\buildtrees\zyre\src\32d83c5294-8833c9e2fa.clean\src\perf_remote.c(83,34): warning: ISO C++11 does not allow conversion from string literal to 'char *' [-Wwritable-strings]
                sending_cookie = "R:SHOUT";