Improve the thread support for VxWorks

Improve the thread support for VxWorks

2019-11-12  Corentin Gay  <gay@adacore.com>
	    Jerome Lambourg  <lambourg@adacore.com>
	    Olivier Hainque  <hainque@adacore.com>

	libgcc/

	* config/t-gthr-vxworks: New file, add all the gthr-vxworks
	sources to LIB2ADDEH.
	* config/t-vxworks: Remove adjustments to LIB2ADDEH.
	* config/t-vxworks7: Likewise.

	* config.host: Append a block at the end of the file to add the
	t-gthr files to the tmake_file list for VxWorks after everything
	else.

	* config/vxlib.c: Rename as gthr-vxworks.c.
	* config/vxlib-tls.c: Rename as gthr-vxworks-tls.c.

	* config/gthr-vxworks.h: Simplify a few comments.  Expose a TAS
	API and a basic error checking API, both internal.  Simplify the
	__gthread_once_t type definition and initializers.  Add sections
	for condition variables support and for the C++0x thread support,
	conditioned against Vx653 for the latter.

	* config/gthr-vxworks.c (__gthread_once): Simplify comments and
	implementation, leveraging the TAS internal API.
	* config/gthr-vxworks-tls.c: Introduce an internal TLS data access
	API, leveraging the general availability of TLS services in VxWorks7
	post SR6xxx.
	(__gthread_setspecific, __gthread_setspecific): Use it.
	(tls_delete_hook): Likewise, and simplify the enter/leave dtor logic.
	* config/gthr-vxworks-cond.c: New file.  GTHREAD_COND variable
	support based on VxWorks primitives.
	* config/gthr-vxworks-thread.c: New file.  GTHREAD_CXX0X support
	based on VxWorks primitives.

Co-Authored-By: Jerome Lambourg <lambourg@adacore.com>
Co-Authored-By: Olivier Hainque <hainque@adacore.com>
From-SVN: r278249