libc: Implement setbuf(), setbuffer(), and setlinebuf()

These are all simple wrappers around setvbuf().

libc/include/stdio.h

@@ -191,6 +191,15 @@ extern "C"
     /* Change a file's buffering mode and internal buffer. */
     int setvbuf(FILE* stream, char* buf, int mode, size_t size);
 
+    /* Change a file's internal buffer. */
+    void setbuf(FILE* stream, char* buf);
+
+    /* Change a file's internal buffer. */
+    void setbuffer(FILE* stream, char* buf, size_t size);
+
+    /* Change a file's buffering mode to line buffered. */
+    void setlinebuf(FILE* stream);
+
 #ifdef __cplusplus
 }
 #endif

libc/src/stdio.cpp

@@ -729,4 +729,19 @@ extern "C"
 
         return 0;
     }
+
+    void setbuf(FILE* stream, char* buf)
+    {
+        setvbuf(stream, buf, buf ? _IOFBF : _IONBF, BUFSIZ);
+    }
+
+    void setbuffer(FILE* stream, char* buf, size_t size)
+    {
+        setvbuf(stream, buf, buf ? _IOFBF : _IONBF, size);
+    }
+
+    void setlinebuf(FILE* stream)
+    {
+        setvbuf(stream, NULL, _IOLBF, 0);
+    }
 }