Fix small documentation mistakes.

Submitted by:	brueffer
Approved by:	kib (mentor)

lib/libc/stdio/setbuf.3

@@ -83,7 +83,7 @@ normally does) it is line buffered.
 The standard error stream
 .Dv stderr
 is always unbuffered.
-Note that these defaults maybe be altered using the
+Note that these defaults may be altered using the
 .Xr stdbuf 1
 utility.
 .Pp

lib/libstdbuf/libstdbuf.3

@@ -43,7 +43,7 @@ an utility,
 .Xr stdbuf 1 ,
 can be used to run a command with the appropriate environment variables.
 .Sh ENVIRONMENT
-Each stream can be configured indepentently through the following
+Each stream can be configured independently through the following
 environment variables (values are defined below):
 .Bl -tag -width size -offset indent
 .It Ev _STDBUF_I