[libpng16] Fixed some nits in contrib/arm-neon/README and comments in

contrib/examples/*.c

contrib/arm-neon/README

@@ -7,7 +7,7 @@ operating system support.  (The information is not available in user mode.)
 HOW TO USE THIS
 ---------------
 
-This directory contains C code fragments which can be included in arm/arm_init.c
+This directory contains C code fragments that can be included in arm/arm_init.c
 by setting the macro PNG_ARM_NEON_FILE to the file name in "" or <> at build
 time.  This setting is not recorded in pnglibconf.h and can be changed simply by
 rebuilding arm/arm_init.o with the required macro definition.
@@ -66,8 +66,8 @@ You may send contributions of new implementations to
 png-mng-implement@sourceforge.net.  Please write code in strict C90 C where
 possible.  Obviously OS dependencies are to be expected.  If you submit code you
 must have the authors permission and it must have a license that is acceptable
-to the current maintainer; in particular that license must permit
-redistribution.
+to the current maintainer; in particular that license must permit modification
+and redistribution.
 
 Please try to make the contribution a single file and give the file a clear and
 unambiguous name that identifies the target OS.  If multiple files really are

contrib/examples/iccfrompng.c

@@ -6,9 +6,9 @@
  * United States.
  *
  * Extract any icc profiles found in the given PNG files.  This is a simple
- * example of a program which extracts information from the header of a PNG file
+ * example of a program that extracts information from the header of a PNG file
  * without processing the image.  Notice that some header information may occur
- * after the image data, textual data and comments are an example; the approach
+ * after the image data. Textual data and comments are an example; the approach
  * in this file won't work reliably for such data because it only looks for the
  * information in the section of the file that preceeds the image data.
  *

contrib/examples/pngpixel.c

@@ -8,7 +8,7 @@
  * Read a single pixel value from a PNG file.
  *
  * This code illustrates basic 'by-row' reading of a PNG file using libpng.
- * Rows are read until a particular pixel is found, the value of this pixel is
+ * Rows are read until a particular pixel is found; the value of this pixel is
  * then printed on stdout.
  *
  * The code illustrates how to do this on interlaced as well as non-interlaced
@@ -56,7 +56,7 @@ component(png_const_bytep row, png_uint_32 x, unsigned int c,
       case 8: return row[0];
       case 16: return (row[0] << 8) + row[1];
       default:
-         /* This should never happen, it indicates a bug in this program or in
+         /* This should never happen; it indicates a bug in this program or in
           * libpng itself:
           */
          fprintf(stderr, "pngpixel: invalid bit depth %u\n", bit_depth);
@@ -132,7 +132,7 @@ print_pixel(png_structp png_ptr, png_infop info_ptr, png_const_bytep row,
          return;
 
       default:
-         png_error(png_ptr, "invalid color type");
+         png_error(png_ptr, "pngpixel: invalid color type");
    }
 }