Add minimal support for QNX to configure.

Recognize QNX and define __QNX__ under it.

Don't use -lpthreads as the thread functions are in libc under QNX.

Use wxX11 by default.

See #11790.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@63664 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/doxygen/mainpages/const_cpp.h

@@ -103,6 +103,7 @@ symbols, although this has not always been followed.
 @itemdef{__LINUX__, Linux}
 @itemdef{__MACH__, Mach-O Architecture (Mac OS X only builds)}
 @itemdef{__OSF__, OSF/1}
+@itemdef{__QNX__, QNX Neutrino RTOS}
 @itemdef{__PALMOS__, PalmOS}
 @itemdef{__SGI__, IRIX}
 @itemdef{__SOLARIS__, Solaris}