Typo fix: replacing it's -> its

Signed-off-by: NBenoit Bourbie <benoit.bourbie@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

INSTALL

@@ -101,7 +101,7 @@ Issues of note:
 	- "openssl" library is used by git-imap-send to use IMAP over SSL.
 	  If you don't need it, use NO_OPENSSL.
 
-	  By default, git uses OpenSSL for SHA1 but it will use it's own
+	  By default, git uses OpenSSL for SHA1 but it will use its own
 	  library (inspired by Mozilla's) with either NO_OPENSSL or
 	  BLK_SHA1.  Also included is a version optimized for PowerPC
 	  (PPC_SHA1).

perl/private-Error.pm

@@ -630,7 +630,7 @@ =head1 CLASS INTERFACE
 =head2 CONSTRUCTORS
 
 The C<Error> object is implemented as a HASH. This HASH is initialized
-with the arguments that are passed to it's constructor. The elements
+with the arguments that are passed to its constructor. The elements
 that are used by, or are retrievable by the C<Error> class are listed
 below, other classes may add to these.
 
@@ -763,7 +763,7 @@ =head1 PRE-DEFINED ERROR CLASSES
 
 =item Error::Simple
 
-This class can be used to hold simple error strings and values. It's
+This class can be used to hold simple error strings and values. Its
 constructor takes two arguments. The first is a text value, the second
 is a numeric value. These values are what will be returned by the
 overload methods.