Revert "Revert "Merge pull request #971 from metropt/update_gyro_rate_ff3""

This reverts commit 817a823da129aa00be66108fe5527d07fdbec9b9.
Initial sensor read after rate change
only set the sample rate on board config, clean-up
fix typo in function description and correct function parameter
Make: create PHONY for standalone

This is good practice for targets that do not create
particular files.
all pios_irq: add PIOS_IRQ_GetInISR() method
GCS/Uploader: set boot timeout to three second

This is the maximum time it should take with the new
bootloader. The old one may still take longer.
pios_com: ensure proper usage of Semaphore_Give depending on context
UAVOFrSkySPortBridge: fixed absence of byte stuffing
UAVOFrSKYSPortBridge: ignore_rx_chars reflects real count of transmitted bytes
UAVOFrSKYSPortBridge: added comment regarding tx buffer size
UAVOFrSKYSPortBridge: added comment regarding checksum calculation
ChibiOS: Pristine import of v2.6.6
ChibiOS: fix GPIOv2 conflict with st libs GPIO_TypeDef
ChibiOS: remove CMSIS arm_math.h to prevent conflict
ChibiOS: disable stm32f30x usb irq relocation for legacy compatibility
pios_semaphore: fix mismatched comment
pios_semaphore: add ChibiOS implementation
pios_semaphore: fix simulation exception
pios_mutex: add ChibiOS implementation