Makefile.unix:  There is a sort command in the 'make savedefconfig' file.  I found that sort behaves differently on different platforms based on the environment variable LC_ALL.  Now, Makefile.unix will force LC_ALL=C just for the sort command so that we can all generate equivalent defconfig files.

Add FPU to xmc4 ostest

* remove +x from makefiles

* preserve .gdbinit across make clean

* add FPU support to ostest on xmc4

* add FPU test to ostest on xmc4

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

Comment out most of 430060e9.  Clean-up some dependencies in top-level Makefile

This reverts commit 430060e9.

That commit has some unexpected side-effects

Makefiles.*: It should be possible to run 'make menuconfig' with no .config and no Make.defs file.  This change removes the dependency on Make.defs, but does not solve the problem of the missing .config file.  Without a .config file, it is not currently possible for the Makefile.* to correctly setup up the symbolic links to directories.

Back out last Makefile.unix change.  After puzzling about this for a while, I moved the definitions to apps/Make.defs.  Also includes some cosmetic changes to GPIO lower half driver comments.

In the menuconfig target, the context dependency was executed before kconfig-mconf.  That was necessary because the link at apps/platform/board needed to be set up before creating the apps/Kconfig file.  Otherwise, the platform Kconfig files would not be included.  But this introduces the chicken-and-egg problem in some configurations.

In particular:  (1) An NX graphics configuration is used that requires auto-generation of source files using cpp, (2) the configuration is set for Linux, but (3) we are running under Cygwin with (4) a Windows native toolchain.  In this case, POSIX-style symbolic links are set up but the Windows native toolchain cannot follow them.

The reason we are running 'make menuconfig' is to change from Linux to Cygwin, but the target fails.  During the context phase, NX runs CPP to generate source files but that fails because the Windows native toolchain cannot follow the links.  Checkmate.

This was fixed by changing all of the make menuconfig (and related) targets.  They no long depend on context being run.  Instead, they depend only on the dirlinks target.  The dirlinks target only sets up the directory links but does not try to run all of the context setup; the compiler is never invoked; no code is autogeneraed; and things work.

Add logic to support custom board directories that include a Kconfig file.  During the context phase of the build, any Kconfig file in the custom board directory is copied into configs/dummy, replacing the existing Kconfig file with the target Kconfig file.

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 does context, pre_config, menuconfig, clean_context.  Not nearly as snappy as it used to be.

Add configuration logic to include a Kconfig file in each custom configuration.  Includes adding a dummy custom board configuration directory.  A consequence of this that each custom board directory will now need to contain a Kconfig file.  NOTE also that the new board directory does not take effect in the configuration menues until the NEXT time you run 'make menuconfig'

Build system: Add 'make oldconfig' target.  Use this option in tools/testbuild.sh.  Add --silent option to tools/refresh.sh so that it can be run in batch without human interaction

tools/cnvwindeps.c:  Need to build this tool even on non-Cygwin platforms (either that or rethink the dependencies).

Fix references to the no-longer-existent misc/ directory in comments, README files, and documentation