In the case dcache write-buffed mode is used (not write-through)
   buffer alignment is required for DMA transfers because
   a) arch_invalidate_dcache could lose buffered writes data
   and b) arch_flush_dcache could corrupt adjacent memory if
   the maddr and the mend+1, the next next address are not on
   ARMV7M_DCACHE_LINESIZE boundaries.

   Updated comment to proper refernce manual for STM32F7 not
   STM32F4.

   Added stm32_dmacapable input paramaters documentation.

stm32f7:rtc Missing semicolon

Approved-by: Gregory Nutt <gnutt@nuttx.org>

STM32L4 DAC: port from STM32.  Note that this does not address the somewhat confusing relation between STM32L4_NDACS and DAC2 config macros that comes from original STM32 code.

readme: more typo fixes

Approved-by: Gregory Nutt <gnutt@nuttx.org>

fix ESP32 gpio enable reg and default UART pin.

Approved-by: Gregory Nutt <gnutt@nuttx.org>

STM32F7: Some STM32F7 builds failed in build testing due to undefined STM32_SRAM1_BASE.  I think that is because stm32_allocateheap.c was not including chip/stm32_memorymap.h

C++: Compilation with recent C++ compiler needs an overloaded delete[] operator that includes a size_t size argument.

ARM: The older ARM7 and ARM9 configurations were determining CFLAGS based on the GCC version 4.x.x or not.  That needx to be extended for 5.x.x and 6.x.x which also behave like 4.x.x.

C++: Compilation with recent C++ compiler needs an overloaded delete operator that includes a size_t size argument.