Remove configs/stm32f746g-disco/netnsh.  It does not build.  Probably a corrupted, hand-editted defconfig file.

STM32 CAN: Clone missing stm32_enterinitmode() and _exitinitmode() from STM32L4.  Don't know if this is write but is needed to compile.

efm32, lcp43, stm32, stm32l4: disable interrupts with NVIC_IRQ_CLEAR

This change fixes a build problem that only occurs when reconfiguring from Linux to Windows or vice-versa.  It is a problem that was present but not usually experienced until two things happened:  (1) The pre_config target was added to run before the menconfig operation and (2) the context target was added before the pre_config target in order to set up the correct symbolic links (in the apps/platform directory) needed by the pre_config target.

But then now if you start with a Linux system and run 'make menuconfig' to switch to Linux, the context target will execute first and set up POSIX style symbolic links before doing the menuconfig.  Then after the menuconfig, the make will fail on Windows if you are using a Windows native toolchain because that native toolchain cannot follow the Cygwin-style symbolic links.

The first here is to also execute the clean_context AFTER executing menuconfig.  A lot more happens now:  It used to be that doing 'make menuconfig' only did the menuconfig operation.  No it doe...

Upstream_nucleo 144

sched/semaphore: Fix setting EINVAL in sem_post() and sem_wait()

Upstream_nucleo 144

Fixed build of SAMV71-XULT/nsh.  With the changes from 26f7b8c9 the build process of the default configuration did not succeed anymore.  This is fixed by this commit.

STM32 CAN: More fixes for compilation errors due to blind leverage of STM32L4 CAN filter IOCTLs to STM32

Upstream_nucleo 144

Upstream_nucleo 144

libc/hex2bin:  Move the portable library portion of apps/system/hex2bin to nuttx/libc/hex2bin where it can be shared with the OS internals.