aded buffer_getc, buffer_getn get n bytes less only if EOF and

buffer_get_token for getting n bytes till finding a termination char or
EOF/error.

buffer/buffer_getc.c

@@ -0,0 +1,12 @@
+#include "byte.h"
+#include "buffer.h"
+
+int buffer_getc(buffer* b,char* x) {
+  if (b->p==b->n) {
+    register int blen;
+    if ((blen=buffer_feed(b))<=0) return blen;
+  }
+  *x=b->x[b->p];
+  ++b->p;
+  return 1;
+}