buffer: remove redundant function

For some reason we ended up with two identical functions: buffer_{clear,terminate}.

buffer.c

@@ -29,10 +29,6 @@ bool buffer_grow(Buffer *buf, size_t size) {
 	return true;
 }
 
-void buffer_truncate(Buffer *buf) {
-	buf->len = 0;
-}
-
 bool buffer_terminate(Buffer *buf) {
 	return !buf->data || buf->len == 0 || buf->data[buf->len-1] == '\0' ||
 	        buffer_append(buf, "\0", 1);

buffer.h

@@ -20,8 +20,6 @@ void buffer_release(Buffer*);
 void buffer_clear(Buffer*);
 /* reserve space to store at least size bytes in this buffer.*/
 bool buffer_grow(Buffer*, size_t size);
-/* truncate buffer, but keep associated memory region for further data */
-void buffer_truncate(Buffer*);
 /* if buffer is not empty, make sure it is NUL terminated */
 bool buffer_terminate(Buffer*);
 /* replace buffer content with given data, growing the buffer if needed */

vis-core.h

@@ -91,7 +91,7 @@ typedef struct {
 typedef Buffer Macro;
 #define macro_init buffer_init
 #define macro_release buffer_release
-#define macro_reset buffer_truncate
+#define macro_reset buffer_clear
 #define macro_append buffer_append0
 
 typedef struct {             /** collects all information until an operator is executed */