Changeset 87f8b01 in rtems for c/src/lib

RTEMS GPIO API definition and implementation.

Changes relative to the previous patch set:

• Moved GPIO pin interrupts to rtems chains, instead of a local linked list;
• Restructured the pin tracking structure, separating the interrupt information for each pin meaning that a pin without any interrupt enabled only requires 8 bytes, while keeping interrupt information (handling information, handler chain control, ...) requires 24 additional bytes (total of 32 bytes per pin with interrupts enabled);
• Added support for 'parallel' pin function assignment, allowing the function assignment to be set for multiple pins in a single GPIO hardware call. If a BSP does not support this feature it becomes a sequence of individual calls per pin. Also added support for GPIO pin groupings, allowing to write and read byte data to a series of pins which behave as a single entity;
• Added bank tracking structure to maintain the bank lock and bank level interrupt information (threaded/normal handling, interrupt counter);
• Changed GPIO settings to BSP defined constants, reducing dynamic memory allocation;
• Switched interrupt tasks for a rtems interrupt server, with the possibility of using normal interrupts (user handlers being called within ISR context).