Fix minor typos in docs and comments.

Documentation/NXGraphicsSubsystem.html

@@ -1037,7 +1037,7 @@ int nxmu_start(int display, int plane);
 </p>
 <p>
   <b>Returned Value:</b>
-  On success zero (<code>OK</code) is returned; -1 (<code>ERROR</code>) is returned on failure with the <code>errno</code> variable to to indicate the nature of the failure.
+  On success zero (<code>OK</code) is returned; -1 (<code>ERROR</code>) is returned on failure with the <code>errno</code> variable set to indicate the nature of the failure.
 </p>
 
 <h3>2.3.4 <a name="nxcallbacks">NX Server Callbacks</a></h3>
@@ -4088,7 +4088,7 @@ enum nx_fontid_e
 </ol>
 <p>
   New Add the font to the NX build system.
-  There are several files that you have to modify to to this.
+  There are several files that you have to modify to do this.
   Look how the build system uses the font CONFIG_NXFONT_SANS23X27 for examaples:
 </p>
 <ol start="5">

Documentation/NuttxPortingGuide.html

@@ -3717,7 +3717,7 @@ void lpwork_restorepriority(uint8_t reqprio);
 </ul>
 <p><b>Description</b>:</p>
 <ul>
-  After an address environment has been established for a task (via <code>up_addrenv_create())</code>, this function may be called to to instantiate that address environment in the virtual address space.
+  After an address environment has been established for a task (via <code>up_addrenv_create())</code>, this function may be called to instantiate that address environment in the virtual address space.
   This might be necessary, for example, to load the code for the task from a file or to access address environment private data.
 </ul>
 <p><b>Input Parameters</b>:</p>
@@ -3742,7 +3742,7 @@ void lpwork_restorepriority(uint8_t reqprio);
 <p><b>Description</b>:</p>
 <ul>
   After an address environment has been temporarily instantiated by <code>up_addrenv_select</code>,
-  this function may be called to to restore the original address environment.
+  this function may be called to restore the original address environment.
 </ul>
 <p><b>Input Parameters</b>:</p>
 <ul>
@@ -4161,7 +4161,7 @@ void nxsched_timer_expiration(void);
 <p><b>Returned Value</b>:</p>
 <ul>
   On success zero (<code>OK</code>) is returned;
-  -1 (<code>ERROR</code>) is returned on failure with the <code>errno</code> variable to to indicate the nature of the failure.
+  -1 (<code>ERROR</code>) is returned on failure with the <code>errno</code> variable set to indicate the nature of the failure.
 </ul>
 
 <h4><a name="boardsmp">4.10 Symmetric Multiprocessing (SMP) Application Interface</a></h4>

Documentation/NuttxUserGuide.html

@@ -484,7 +484,7 @@ int task_delete(pid_t pid);
 </p>
 <p>
   The logic in this function only deletes non-running tasks.
-  If the  <code>pid</code> parameter refers to to the currently runing task, then processing is redirected to <code>exit()</code>.
+  If the <code>pid</code> parameter refers to the currently running task, then processing is redirected to <code>exit()</code>.
   This can only happen if a task calls <code>task_delete()</code> in order to delete itself.
 </p>
 <p>