Documentation: remove duplicated words

Remove many duplicated words under Documentation/ and do other small
cleanups.

Examples:
        "and and" --> "and"
        "in in" --> "in"
        "the the" --> "the"
        "the the" --> "to the"
        ...

Signed-off-by: Paolo Ornati <ornati@fastwebnet.it>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
diff --git a/Documentation/unshare.txt b/Documentation/unshare.txt
index 90a5e9e..a864351 100644
--- a/Documentation/unshare.txt
+++ b/Documentation/unshare.txt
@@ -260,7 +260,7 @@
        a pointer to it.
 
   7.4) Appropriately modify architecture specific code to register the
-       the new system call.
+       new system call.
 
 8) Test Specification
 ---------------------