CheckStructHasMember: Add support for C++

Previously if headers required to check if a struct has a member can be
compiled with C++ compiler only, the check would fail because the C
compiler fails.  As a consequence, the result variable would be set to
false, even if the struct has that particular member.

Teach CHECK_STRUCT_HAS_MEMBER to accept a new optional argument LANGUAGE
that allows one to explicitly set the compiler to use.  The new
signature is therefore:

  CHECK_STRUCT_HAS_MEMBER (<struct> <member> <header> <variable>
                           [LANGUAGE <language>])

1 files changed, 10 insertions, 0 deletions

diff --git a/Tests/RunCMake/CheckModules/CheckStructHasMemberUnknownLanguage-stderr.txt b/Tests/RunCMake/CheckModules/CheckStructHasMemberUnknownLanguage-stderr.txt
new file mode 100644
index 0000000..ba9e313
--- /dev/null
+++ b/Tests/RunCMake/CheckModules/CheckStructHasMemberUnknownLanguage-stderr.txt
@@ -0,0 +1,10 @@
+CMake Error at .*/Modules/CheckStructHasMember.cmake:[0-9]+. \(message\):
+  Unknown language:
+
+    FORTRAN
+
+  Supported languages: C, CXX.
+
+Call Stack \(most recent call first\):
+  CheckStructHasMemberUnknownLanguage.cmake:[0-9]+ \(check_struct_has_member\)
+  CMakeLists.txt:[0-9]+ \(include\)