gdbstub: move into its own sub directory

This is in preparation of future refactoring as well as cleaning up
the source tree. Aside from the minor tweaks to meson and trace.h this
is pure code motion.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220929114231.583801-43-alex.bennee@linaro.org>
diff --git a/meson.build b/meson.build
index 536e819..b686dfe 100644
--- a/meson.build
+++ b/meson.build
@@ -2863,6 +2863,7 @@
   'qom',
   'monitor',
   'util',
+  'gdbstub',
 ]
 if have_linux_user
   trace_events_subdirs += [ 'linux-user' ]
@@ -2986,6 +2987,7 @@
 subdir('crypto')
 subdir('ui')
 subdir('hw')
+subdir('gdbstub')
 
 
 if enable_modules
@@ -3063,7 +3065,7 @@
 subdir('softmmu')
 
 common_ss.add(capstone)
-specific_ss.add(files('cpu.c', 'disas.c', 'gdbstub.c'), capstone)
+specific_ss.add(files('cpu.c', 'disas.c'), capstone)
 
 # Work around a gcc bug/misfeature wherein constant propagation looks
 # through an alias: