Make ctxobj.exp and print-file-var.exp work on all platforms.

Make ctxobj.exp and print-file-var.exp work on all platforms.

This patch adjusts the testing strategy used in a couple of testcases
where we are trying to print the value of a global variable defined
at multiple locations.  The problem is that the actual value depends
on the platform.  So instead of hard-coding the expected value in
the testcase script, we use local variables (in the inferior) holding
the correct value, and we compare the global variable's value with
the local variable's value.

gdb/testsuite/ChangeLog:

        * gdb.base/ctxobj-f.c (GET_VERSION): Introduce local variable
        and add comment.
        * gdb.base/ctxobj-m.c (main): Rewrite, and add comment.
        * gdb.base/ctxobj.exp: Insert breakpoint in ctxobj-f.c using
        "STOP" marker.  Adjust testing strategy to make it work on
        all targets.

        * gdb.base/print-file-var-main.c (main): Rewrite using local
        variables and adjust get_version_2's return value check.
        Add small comment.
        * gdb.base/print-file-var.exp: Insert breakpoint using "STOP"
        marker.  Adjust testing strategy to make it work on all targets.