system_error: Use noexcept.

2011-07-20  Paolo Carlini  <paolo.carlini@oracle.com>

	* include/std/system_error: Use noexcept.
	* src/system_error.cc: Likewise.
	* testsuite/19_diagnostics/error_condition/modifiers/39881.cc: Adjust.
	* testsuite/19_diagnostics/error_condition/cons/39881.cc: Likewise.
	* testsuite/19_diagnostics/error_code/modifiers/39882.cc: Likewise.
	* testsuite/19_diagnostics/error_code/cons/39882.cc: Likewise.
	* testsuite/util/testsuite_error.h: Likewise.

	* include/std/system_error (error_code::error_code(_ErrorCodeEnum)):
	Use enable_if on template parameter default.
	(error_condition::error_condition(_ErrorConditionEnum)): Likewise.

From-SVN: r176529