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_get_token.c

@@ -0,0 +1,15 @@
+#include "byte.h"
+#include "buffer.h"
+#include "scan.h"
+
+int buffer_get_token(buffer* b,char* x,unsigned int len,const char* charset,unsigned int setlen) {
+  int blen;
+
+  for (blen=0;blen<len;++blen) {
+    if ((r=buffer_getc(b,*x))<0) return r;
+    if (r==0) return blen;
+    if (byte_chr(charset,clen,*x)<clen) return blen;
+    ++x;
+  }
+  return blen;
+}