Move a test from static-assert.cpp to DeclPrinterTest

It's better not to rely on the diagnostics engine to pretty print the
argument to decltype.  Instead, exercise the functionality in
DeclPrinterTest.

llvm-svn: 239197
diff --git a/clang/lib/ASTMatchers/Dynamic/Registry.cpp b/clang/lib/ASTMatchers/Dynamic/Registry.cpp
index 04d3a32..59c204d 100644
--- a/clang/lib/ASTMatchers/Dynamic/Registry.cpp
+++ b/clang/lib/ASTMatchers/Dynamic/Registry.cpp
@@ -311,6 +311,7 @@
   REGISTER_MATCHER(specifiesTypeLoc);
   REGISTER_MATCHER(statementCountIs);
   REGISTER_MATCHER(staticCastExpr);
+  REGISTER_MATCHER(staticAssertDecl);
   REGISTER_MATCHER(stmt);
   REGISTER_MATCHER(stringLiteral);
   REGISTER_MATCHER(substNonTypeTemplateParmExpr);