[Ada] Crash on timed entry call with a delay given by a type conversion

[Ada] Crash on timed entry call with a delay given by a type conversion

This patch fixes a compiler crash in the compiler on a timed entry call
whose delay expression is a type conversion, when FLoat_Overflow checks
are enabled.

2019-07-08  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* exp_ch9.adb (Expand_N_Timed_Entry_Call): Do not insert twice
	the assignment statement that computes the delay value, to
	prevent improper tree sharing when the value is a type
	conversion and Float_Overflow checks are enabled.

gcc/testsuite/

	* gnat.dg/entry1.adb, gnat.dg/entry1.ads: New testcase.

From-SVN: r273210