RFR: Remove execinfo debug code from XToolkit.c

[Mikael Vidstedt]

XToolkit.c has some linux specific debug code in it which is effectively dead. The debug code depends on backtracing functionality from execinfo.h, but musl does not implement/support execinfo.h.

Since the code is dead, I chose to remove it. In case it turns out that this debugging code gets used a lot when chasing down bugs etc. we’ll have to look at how to support it on musl, or perhaps only enable it if execinfo.h is available.

http://cr.openjdk.java.net/~mikael/webrevs/portola/execinfo/webrev.00/jdk/webrev/

Cheers,
Mikael