* configure.in: add tests for figuring out whether buffered data

is available in a FILE structure, which is needed by char-ready.

* acconfig.h: define FILE_CNT_FIELD, FILE_CNT_GPTR and
FILE_CNT_READPTR.

* simpos.c (scm_getenv): renamed from scm_sys_getenv.  Throw
exceptions using misc_error instead of syserror.  It seems a bit
odd to throw an exception if a string can't be found in the
environment, but it's consistent with open-file, stat etc.
(simpos.h): remove sys_ from getenv.

* posix.c (scm_putenv): renamed from scm_sys_putenv.  If an error
occurs, throw an error instead of returning errno.  Return value
is now unspecified.
(numerous in posix.c and posix.h): removed superfluous sys_ from names.

libguile/acconfig.h

@@ -12,6 +12,26 @@
    configure.in for more details.  */
 #undef HAVE_FD_SETTER
 
+/* Define this if your system has a way to set a stdio stream's file
+   descriptor.  You should also copy fd.h.in to fd.h, and give the
+   macro SET_FILE_FD_FIELD an appropriate definition.  See
+   configure.in for more details.  */
+#undef HAVE_FD_SETTER
+
+/* Set this to the name of a field in FILE which contains the number
+   of buffered characters waiting to be read.  */
+#undef FILE_CNT_FIELD
+
+/* Define this if your stdio has _gptr and _egptr fields which can
+   be compared to give the number of buffered characters waiting to
+   be read.  */
+#undef FILE_CNT_GPTR
+
+/* Define this if your stdio has _IO_read_ptr and _IO_read_end fields
+   which can be compared to give the number of buffered characters
+   waiting to be read.  */
+#undef FILE_CNT_READPTR
+
 /* Define this if your system defines struct linger, for use with the
    getsockopt and setsockopt system calls.  */
 #undef HAVE_STRUCT_LINGER