Fix typos in sample comments

Closes https://github.com/wxWidgets/wxWidgets/pull/2513

samples/opengl/isosurf/isosurf.cpp

@@ -197,7 +197,7 @@ void TestGLCanvas::LoadSurface(const wxString& filename)
     }
 
     {
-        // we suppose to have in input a text file containing floating numbers
+        // we are supposed to have as input a text file containing floating numbers
         // space/newline-separated... first 3 numbers are the coordinates of a
         // vertex and the following 3 are the relative vertex normal and so on...
 

samples/opengl/pyramid/mathstuff.h

@@ -11,7 +11,7 @@
   #define MATHSTUFF_H
 
 //NOTE:
-// glm library is great for handling matrices and vectors in a OpenGL style, see
+// glm library is great for handling matrices and vectors in an OpenGL style, see
 // http://glm.g-truc.net/
 // But it's too large for this simple sample. I coded on my own the maths needed.
 

samples/opengl/pyramid/oglstuff.cpp

@@ -42,7 +42,7 @@ bool MyOnGLError(int err, const GLchar* glMsg = NULL)
 
 // We do calculations with 'doubles'. We pass 'GLFloats' to the shaders
 // because OGL added 'doubles' since OGL 4.0, and this sample is for 3.2
-// Due to asynchronous nature of OGL, we can't not trust in the passed matrix
+// Due to asynchronous nature of OGL, we can't trust in the passed matrix
 // to be stored by GPU before the passing-function returns. So we don't use
 // temporary storage, but dedicated matrices
 void SetAsGLFloat4x4(double *matD, GLfloat *matF, int msize)
@@ -352,7 +352,7 @@ bool myOGLShaders::AskUnifLocations()
         GLint glret = glGetUniformLocation(m_proId, it->name.c_str());
         if ( glret == -1 )
         {
-            // Return now, this GPU program can not be used because we will
+            // Return now, this GPU program cannot be used because we will
             // pass data to unknown/unused uniform locations
             return false;
         }

samples/opengl/pyramid/oglstuff.h

@@ -50,7 +50,7 @@
 
   I decided to keep apart all of this from wxWidgets. You won't find anything
   related to wxWidgets in the oglstuff[.h][.cpp] files.
-  That's why I use std::vector and std:string instead of those provided by wx.
+  That's why I use std::vector and std::string instead of those provided by wx.
 */
 
 

samples/opengl/pyramid/pyramid.cpp

@@ -273,7 +273,7 @@ void fOGLErrHandler(int err, int glerr, const GLchar* glMsg)
 
 // Creates a 4-bytes-per-pixel, RGBA array from a wxImage.
 // If the image has alpha channel, it's used. If not, pixels with 'cTrans' color
-// get 'cAlpha' alpha; an the rest of pixels get alpha=255 (opaque).
+// get 'cAlpha' alpha; and the rest of pixels get alpha=255 (opaque).
 //
 // NOTE: The returned pointer must be deleted somewhere in the app.
 unsigned char* MyImgToArray(const wxImage& img, const wxColour& cTrans, unsigned char cAlpha)