Fix null byte handling in strchr().

As mentioned in the strchr() comment and the ISO C99 standard,
"The terminating null byte is considered to be part of the string."

In practise this means that strchr(str, '\0'); should return a pointer
to the end of the string. The old version in NuttX returned NULL instead.

The correct behaviour is relied upon by e.g. minini library.
mkfatfs for FAT32 wrote the boot code in wrong place.

This caused mkfatfs to generate slightly corrupted filesystems.
In practise, this caused Windows to present the "Scan and Fix" prompt
every time the device was plugged in.
NxWidgets bitmap_converter.py: Fix bug when image width > 255.
NxWidgets: Fix typo CScollbarPanel -> CScrollbarPanel.
CGlyphButton: Generate action event, like CButton does.
CGlyphButton: Don't draw outside the bitmap size.

Previously CGlyphButton would give its own size to drawBitmap().
It makes more sense to draw only the actual size of the bitmap, otherwise
garbage from memory will be shown.

Also fixes the bitmapX and bitmapY to place the bitmap inside the button
like the comments say it should do.
Add CONFIG_NXWM_TASKBAR_NO_BORDER as an option
Add function to check if CNxTimer is running
CNxWidget: allow overriding checkCollision()