Remove "parse error" in favor of more descriptive diagnostics.

In a few cases clang emitted a rather content-free diagnostic: 'parse error'.
This change replaces two actual cases (template parameter parsing and K&R
parameter declaration parsing) with more specific diagnostics and removes a
third dead case of this in the BalancedDelimiterTracker (the ctor already
checked the invariant necessary to ensure that the diag::parse_error was never
actually used).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@154224 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Parser/cxx-template-decl.cpp b/test/Parser/cxx-template-decl.cpp
index 870be93..be1f81e 100644
--- a/test/Parser/cxx-template-decl.cpp
+++ b/test/Parser/cxx-template-decl.cpp
@@ -6,7 +6,7 @@
                         // expected-error {{does not refer}}
 export template x;      // expected-error {{expected '<' after 'template'}}
 export template<class T> class x0; // expected-warning {{exported templates are unsupported}}
-template < ;            // expected-error {{parse error}} \
+template < ;            // expected-error {{expected template parameter}} \
 // expected-error{{expected ',' or '>' in template-parameter-list}} \
 // expected-warning {{declaration does not declare anything}}
 template <template X> struct Err1; // expected-error {{expected '<' after 'template'}} \