Standard I/O streams open for reading and writing

[gwyn at brl-vld]

From:      Doug Gwyn (VLD/VMB) <gwyn at brl-vld>

The real problem with "r+", "w+", "a+" modes is that one loses buffering.
The simplest fix would involve making either the getc() or putc() buffer
count proceed in the opposite direction.  (Whitesmiths does this in their
buffered i/o package.)  Unfortunately the test in the getc() or putc()
macro then is no longer a test against zero.