Bump compiler plugins Clang baseline to 5.0.2

...as discussed at
<https://lists.freedesktop.org/archives/libreoffice/2018-November/081435.html>
"minutes of ESC call ..."

Change-Id: Ia053da171d59747984546f38e19da808825b4f79
Reviewed-on: https://gerrit.libreoffice.org/63832
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

compilerplugins/clang/test/staticconstfield.cxx

@@ -47,7 +47,6 @@ class Class4
     }
 };
 
-#if CLANG_VERSION >= 50000 // Expr::EvaluateAsFloat
 class Class5
 {
     enum class Enum
@@ -77,7 +76,6 @@ class Class5
         (void)m_fielda4;
     }
 };
-#endif
 
 // no warning expected
 class Class6