getc/ungetc in assemblers; BUFSIZ everywhere.

Fixes #67.

R=r
https://golang.org/cl/154068

src/cmd/5a/a.h

@@ -37,6 +37,10 @@
 #define	EXTERN	extern
 #endif
 
+#define	getc	aagetc
+#define	ungetc	aaungetc
+#define	BUFSIZ	AABUFSIZ
+
 typedef	struct	Sym	Sym;
 typedef	struct	Gen	Gen;
 typedef	struct	Io	Io;

src/cmd/6a/a.h

@@ -38,6 +38,10 @@
 #define	EXTERN	extern
 #endif
 
+#define	getc	aagetc
+#define	ungetc	aaungetc
+#define	BUFSIZ	AABUFSIZ
+
 typedef	struct	Sym	Sym;
 typedef	struct	Ref	Ref;
 typedef	struct	Gen	Gen;

src/cmd/8a/a.h

@@ -38,6 +38,10 @@
 #define	EXTERN	extern
 #endif
 
+#define	getc	aagetc
+#define	ungetc	aaungetc
+#define	BUFSIZ	AABUFSIZ
+
 typedef	struct	Sym	Sym;
 typedef	struct	Ref	Ref;
 typedef	struct	Gen	Gen;

src/cmd/cc/cc.h

@@ -41,6 +41,7 @@
 
 #define	getc	ccgetc
 #define	ungetc	ccungetc
+#define	BUFSIZ	GCBUFSIZ
 
 typedef	struct	Node	Node;
 typedef	struct	Sym	Sym;

src/cmd/gc/go.h

@@ -17,6 +17,7 @@
 
 #define	getc	gcgetc
 #define	ungetc	gcungetc
+#define	BUFSIZ	GCBUFSIZ
 
 enum
 {