Added new msprf24_rx_pending() to ease the check of inbound RX FIFO data even when no RX IRQ is raised.
SPI support for G2xx4/G2xx5 chips.
Added support for +7dBm mode available in "SI24R1" Taiwanese knockoff-chipsets.  Use RF24_POWER_7DBM for the output power.
Fixing a supposed bug in SI24R1 modules; CE pin is now raised during the 5ms "startup" period for POWERDOWN->Standby_I transition