Revert "Work around weird behavior in GCC 4.8 where it thinks this destructor's…

Revert "Work around weird behavior in GCC 4.8 where it thinks this destructor's declaration and definition hase mismatching noexcept specs even though neither one has a noexcept spec at all."

This reverts commit c088dd95.

Reverted in favor of dwrensha's more complete fix.

c++/src/capnp/compiler/lexer.c++

@@ -269,5 +269,7 @@ Lexer::Lexer(Orphanage orphanageParam, const ErrorReporter& errorReporterParam)
   parsers.emptySpace = commentsAndWhitespace;
 }
 
+Lexer::~Lexer() {}
+
 }  // namespace compiler
 }  // namespace capnp

c++/src/capnp/compiler/lexer.h

@@ -53,6 +53,8 @@ public:
   // `orphanage` is used to allocate Cap'n Proto message objects in the result.  `inputStart` is
   // a pointer to the beginning of the input, used to compute byte offsets.
 
+  ~Lexer();
+
   class ParserInput: public kj::parse::IteratorInput<char, const char*> {
     // Like IteratorInput<char, const char*> except that positions are measured as byte offsets
     // rather than pointers.