sp/configure.in runs AC_C_CONST and AC_C_INLINE, which are C
specific tests, after setting AC_LANG_CPLUSPLUS
const and inline are NOT optional in C++, though they are in
C, hence the _C_ in their names!
The fix is to remove these tests from configure.in and run
autoconf before re-packaging.
fixed in 1.0.9-5 and later.