Update regression tests to change GCC version from 10 to 13

Storing test results from a newer version than GCC 10 also paves the way to change the minimum supported GCC from 10 to 11, so we can take a dependency on the GCC 11 `requires`-in-declaration bugfix that wasn't backported to GCC 10

This commit also catches up on test output that hadn't been captured for MSVC and Clang

Author: hsutter

regression-tests/test-results/gcc-10/mixed-allcpp1-hello.cpp.output renamed to regression-tests/test-results/clang-12/pure2-bugfix-for-requires-clause-unbraced-function-initializer.cpp.execution

@@ -1,4 +1,4 @@
-c++ (GCC) 13.1.1 20230429
+gcc (GCC) 13.1.1 20230614 (Red Hat 13.1.1-4)
 Copyright (C) 2023 Free Software Foundation, Inc.
 This is free software; see the source for copying conditions.  There is NO
 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

regression-tests/test-results/gcc-10/mixed-as-for-variant-20-types.cpp.output renamed to regression-tests/test-results/clang-12/pure2-bugfix-for-requires-clause-unbraced-function-initializer.cpp.output

@@ -1,15 +1,15 @@
-# This is intended to be run in the /test-results/gcc-10 subdirectory
-# in a Linux shell with g++-10 installed
+# This is intended to be run in the /test-results/gcc-13 subdirectory
+# in a Linux shell with gcc 13 installed
 #
 cp ../*.cpp .
 rm -f *.output
 count=0
 exe_count=0
-g++-10 --version > gcc-version.output 2>&1
+gcc --version > gcc-version.output 2>&1
 for f in *.cpp
 do
-    printf "Starting g++-10 %s\n" "$f"
-    g++-10 -I../../../include -std=c++20 -pthread -o test.exe $f > $f.output 2>&1
+    printf "Starting gcc 13 %s\n" "$f"
+    g++ -I../../../include -std=c++20 -pthread -o test.exe $f > $f.output 2>&1
     rm -f $f
     let count=count+1
     if test -f "test.exe"; then

regression-tests/test-results/gcc-10/gcc-version.output

@@ -0,0 +1 @@
+Hello Freddy with UFCS!

regression-tests/test-results/gcc-10/xyzzy

@@ -0,0 +1 @@
+pure2-bugfix-for-requires-clause-unbraced-function-initializer.cpp