* inline.h: #include "libguile/__scm.h" at the top. Change code

* inline.h: #include "libguile/__scm.h" at the top.  Change code
to use SCM_C_INLINE and SCM_INLINE_C_INCLUDINT_INLINE_H to decide
what to do instead of creating a new public #define.  Rename usage
of USE_COOP_THREADS to SCM_USE_COOP_THREADS.  Rename usage of
USE_NULL_THREADS to SCM_USE_NULL_THREADS.  Rename usage of
USE_COPT_THREADS to SCM_USE_COPT_THREADS.

* inline.c: rearrange handling -- now we just #define
SCM_INLINE_C_INCLUDING_INLINE_H to 1 and #include
"libguile/inline.h".  scmconfig.h will define SCM_C_INLINE as
appropriate, and we use that in inline.h along with the above
define to determine how to respond.