libstdc++: Remove trailing whitespace from dejagnu files
Also fix the name of a source file used by an effective target check.
libstdc++-v3/ChangeLog:
* testsuite/config/default.exp: Remove trailing whitespace.
* testsuite/lib/dg-options.exp: Likewise.
* testsuite/lib/prune.exp: Likewise.
* testsuite/libstdc++-abi/abi.exp: Likewise.
* testsuite/libstdc++-dg/conformance.exp: Likewise.
* testsuite/libstdc++-prettyprinters/prettyprinters.exp:
Likewise.
* testsuite/libstdc++-xmethods/xmethods.exp: Likewise.
* testsuite/lib/libstdc++.exp: Likewise.
(check_v3_target_c_std): Fix filename for temporary source file.