ipa-devirt: check precision mismatch of enum values [PR101396]

ipa-devirt: check precision mismatch of enum values [PR101396]

We are comparing enum values (in wide_int) to check ODR violation.
However, if we compare two wide_int values with different precision,
we'll trigger an assert, leading to ICE.  With enum-base introduced
in C++11, it's easy to sink into this situation.

To fix the issue, we need to explicitly check this kind of mismatch,
and emit a proper warning message if there is such one.

gcc/

	PR ipa/101396
	* ipa-devirt.c (ipa_odr_read_section): Compare the precision of
	  enum values, and emit a warning if they mismatch.

gcc/testsuite/

	PR ipa/101396
	* g++.dg/lto/pr101396_0.C: New test.
	* g++.dg/lto/pr101396_1.C: New test.