Merge DMD r294: bugzilla 2816 Sudden-death static assert is not...

bugzilla 2816 Sudden-death static assert is not very useful.
---
 dmd/expression.h   |   12 ++++++
 dmd/staticassert.c |   10 +---
 dmd/template.c     |  108 ++++++++++++++++++++++++++++++++++++++++++++++++----
 dmd/template.h     |    2 +
 4 files changed, 117 insertions(+), 15 deletions(-)

dmd/template.h

@@ -89,6 +89,8 @@ struct TemplateDeclaration : ScopeDsymbol
     TemplateTupleParameter *isVariadic();
     int isOverloadable();
 
+    void makeParamNamesVisibleInConstraint(Scope *paramscope);
+
 #if IN_LLVM
     // LDC
     std::string intrinsicName;