drivers/modem/u-blox.c and include/nuttx/drivers/u-blox.h:  Add an upper half driver for the U-Blox Modem.  From  Vladimir Komendantskiy

Move xyz_cxxinitialize.c from nuttx/configs/abc/src to apps/platform/abc/ (where xyz is the processor family and abc is the board)

Driver for the  24-Bit Differential Input ADC ADS1242 that communicates via SPI with a MCU. Reading the ADC conversion result as well as configuring the ADC, setting the input channel, etc. is implemented via ioctl calls. However, it does not yet implement the standard ADC interface.

fs/vfs/fs_poll.c: Fix handling of sem_tickwait() return value sem_tickwait() does not return an -1+errno, it returns a negated errno value.  Noted by Freddie Chopin.