libc-symbols.h: remove unused macros

Beside weak_hidden_alias/declare_symbol_alias/hidden_data_ver, many
*_hidden_* macros are removed.  If there is a rare need to use one, one
may write something like `#if IS_IN (libm)\nhidden_def (...)\n#endif`
instead.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>