Lots of -Wunused-command-line-argument warnings from clang

[Sven Joachim]

Building ncurses with clang produces the following warning (line-wrapped
for readability) on every invocation of the compiler:

,----
| clang: warning: argument unused during compilation:
| '--param max-inline-insns-single=1200' [-Wunused-command-line-argument]
`----

It goes without saying that this makes build logs pretty much
unreadable. :-(

There are CF_CLANG_COMPILER and CF_C_INLINE functions in aclocal.m4
which I think are meant to avoid this, but it does not work for me.
Tested with clang-8 and clang-7 on Debian unstable, but I think the
problem had been around for quite a while already.  I did not specify
any fancy configure options, just ran

,----
| $ ./configure CC=clang-7 CXX=clang++-7
`----

Any ideas?

Cheers,
       Sven