gcc 15 and C23 force some union trickery on buffer.h :-(

add a few buffer_init*_forread variants to pretend we have type safety
  make sure buffer_init_staticcontents handles flushing attempts

buffer/buffer_init_write.3

@@ -0,0 +1,14 @@
+.TH buffer_init_write 3
+.SH NAME
+buffer_init_write \- initialize buffer structure
+.SH SYNTAX
+.B #include <libowfat/buffer.h>
+
+void \fBbuffer_init_write\fR(buffer &\fIb\fR,
+                int \fIfd\fR, char* \fIy\fR, size_t \fIylen\fR);
+
+.SH DESCRIPTION
+buffer_init_read is equivalent to calling buffer_init with write(2) as op.
+
+.SH "SEE ALSO"
+buffer_init(3), buffer(3), buffer_init_read(3)