Regressions on master at commit r11-7609 vs commit r11-7600 on Linux/x86_64

[H.J. Lu]

New failures:
FAIL: g++.dg/modules/xtreme-header-3_c.C -std=c++2a (internal compiler error)
FAIL: g++.dg/modules/xtreme-header-3_c.C -std=c++2a (test for excess errors)
FAIL: g++.dg/modules/xtreme-header-4_c.C -std=c++2b (internal compiler error)
FAIL: g++.dg/modules/xtreme-header-4_c.C -std=c++2b (test for excess errors)

New passes: