gdb/testsuite: resolve remaining duplicate test names in gdb.cp/*.exp

gdb/testsuite: resolve remaining duplicate test names in gdb.cp/*.exp

This commit resolves the remaining duplicate test names in
gdb.cp/*.exp.  These are all the easy duplicates, I'm either giving
tests a new, unique name, extending an existing name to make it
unique, or changing an existing name to better reflect what the test
is actually doing, and thus, making this test name unique.

There should be no change in what is tested after this commit.

gdb/testsuite/ChangeLog:

	* gdb.cp/breakpoint.exp: Extend test names to make them unique.
	* gdb.cp/casts.exp: Give tests unique names.
	* gdb.cp/filename.exp: Likewise.
	* gdb.cp/gdb2495.exp: Likewise.
	* gdb.cp/mb-ctor.exp: Extend test names to make them unique.
	* gdb.cp/misc.exp: Rename test to make it unique.
	* gdb.cp/nsnested.exp: Give tests unique names.
	* gdb.cp/ovldbreak.exp: Likewise.
	* gdb.cp/pr17494.exp: Rename test to reflect what is actually
	being tested.  This also removes the duplicate test name.
	* gdb.cp/ref-types.exp: Likewise.
	* gdb.cp/temargs.exp: Likewise.