partially revert change to <bio.h>, reinstating the definition
of BGETC.  this is necesary because the string library has a sneaky
ifdef that hides a dependency on <bio.h>.  rather than hunt this down,
do just the minimum to keep the string library compiling.

Reference: /n/atom/patch/applied/stringlibinclude
Date: Sun May 25 02:55:15 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/include/bio.h	Sun May 25 02:52:57 2014
+++ /sys/include/bio.h	Sun May 25 02:52:58 2014
@@ -40,6 +40,9 @@
 	uchar	b[Bungetsize+Bsize];
 };
 
+/* Dregs, the string library has a sneaky ifdef */
+#define	BGETC		fixthestringlibrary
+
 int	Bbuffered(Biobufhdr*);
 int	Bfildes(Biobufhdr*);
 int	Bflush(Biobufhdr*);