misc: Spelling and grammar fixes in comments

* it's -> its
* grammar fix in ui/vnc-enc-zywrle.h
Signed-off-by: NStefan Weil <sw@weilnetz.de>
Reviewed-by: NDon Koch <dkoch@verizon.com>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

qapi-schema.json

@@ -1914,7 +1914,7 @@
 #
 # Since: 0.14.0
 #
-# Notes: This command only exists as a stop-gap.  It's use is highly
+# Notes: This command only exists as a stop-gap.  Its use is highly
 #        discouraged.  The semantics of this command are not guaranteed.
 #
 #        Known limitations:

slirp/if.c

@@ -142,7 +142,7 @@ diddit:
 
 /*
  * Send a packet
- * We choose a packet based on it's position in the output queues;
+ * We choose a packet based on its position in the output queues;
  * If there are packets on the fastq, they are sent FIFO, before
  * everything else.  Otherwise we choose the first packet from the
  * batchq and send it.  the next packet chosen will be from the session

ui/vnc-enc-zywrle.h

@@ -305,7 +305,7 @@ static inline void harr(int8_t *px0, int8_t *px1)
    |L1H0H1H0|L1H0H1H0|L1H0H1H0|L1H0H1H0| : level 1
 
  In this method, H/L and X0/X1 is always same position.
- This lead us to more speed and less memory.
+ This leads us to more speed and less memory.
  Of cause, the result of both method is quite same
  because it's only difference that coefficient position.
 */