This patch fixes an issue whereby an expression within an expression
function declaration or completion without proper parenthesization is
incorrectly accepted by the compiler.

2018-01-11  Justin Squirek  <squirek@adacore.com>

gcc/ada/

	* par-ch6.adb (Scan_Body_Or_Expression_Function): Add additional check
	to make sure a given expression function is properly parenthesized.

gcc/testsuite/

	* gnat.dg/expr_func4.adb: New testcase.

From-SVN: r256517