bitset: use AC_C_INLINE

[Bruno Haible]

The files
  lib/bitset.h
  lib/bitset.c
  lib/bitset/array.c
  lib/bitset/list.c
  lib/bitset/table.c
  lib/bitset/vector.c
use 'static inline'. To prevent compilation errors with old compilers or with
"gcc -ansi" or such, configure needs to execute AC_C_INLINE.


2020-07-03  Bruno Haible  <bruno@clisp.org>

        bitset: Make sure the compiler does not barf on 'inline'.
        * modules/bitset (configure.ac): New section.

diff --git a/modules/bitset b/modules/bitset
index 20c6806..21cde24 100644
--- a/modules/bitset
+++ b/modules/bitset
@@ -24,6 +24,9 @@ gettext-h
 obstack
 xalloc
 
+configure.ac:
+AC_REQUIRE([AC_C_INLINE])
+
 Makefile.am:
 lib_SOURCES += bitset.c bitset/array.c bitset/stats.c \
   bitset/table.c bitset/list.c bitset/vector.c