Minor Syntax Issues in the `/libpng/contrib/gregbook`

[Gwihwan-Go]

Hi! There are some minor grammar issues in the /libpng/contrib/gregbook

/libpng/contrib/gregbook/readpng.c:269:16: 
[error:[Unmatched '('. Configuration: ''. [syntaxError]
[0mfprintf(stderr, "readpng:  image_data buffer would be too large\n",

/libpng/contrib/gregbook/rpng-win.c:190:5: 
[warning:[Return value of function freopen() is not used. 
[ignoredReturnValue][0mfreopen("CONOUT$", "a", stderr);

[1m../libpng/contrib/gregbook/rpng-win.c:596:5: 
[warning:[%ld in format string (no. 1) requires 'long' but the argument type is 'unsigned long'. [invalidPrintfArgType_sint]
[Trace((stderr, "(width = %ld, rowbytes = %ld, wimage_rowbytes = %d)\n",