gdb: Avoid trailing whitespace when pretty printing

gdb: Avoid trailing whitespace when pretty printing

While writing a new test for 'set print pretty on' I spotted that GDB
will sometimes add a trailing whitespace character when pretty
printing.  This commit removes the trailing whitespace and updates the
expected results in one tests where this was an issue.

I've added an extra test for 'set print pretty on' as it doesn't seem
to have much testing.

gdb/ChangeLog:

	* cp-valprint.c (cp_print_value_fields): Don't print trailing
	whitespace when pretty printing is on.

gdb/testsuite/ChangeLog:

	* gdb.base/finish-pretty.exp: Update expected results.
	* gdb.base/pretty-print.c: New file.
	* gdb.base/pretty-print.exp: New file.