Enable or disable terminal styling. Styling is enabled by default
on most hosts, but disabled by default when in batch mode.
+set style sources [on|off]
+show style sources
+ Enable or disable source code styling. Source code styling is
+ enabled by default, but only takes effect if styling in general is
+ enabled, and if GDB was linked with GNU Source Highlight.
+
set style filename foreground COLOR
set style filename background COLOR
set style filename intensity VALUE