Tracepoints and range stepping are independent features. This patch
skips the gdb.trace/range-stepping.exp test case if the target does not
support range stepping.
gdb/testsuite/ChangeLog:
* gdb.base/range-stepping.exp (gdb_range_stepping_enabled):
Move it to ...
* lib/range-stepping-support.exp (gdb_range_stepping_enabled):
... here.
* gdb.trace/range-stepping.exp: Check that the target supports
range stepping.