[clang-tools-extra] Remove redundant declarations (NFC) (#166894)

In C++17, static constexpr members are implicitly inline, so they no
longer require an out-of-line definition.

Identified with readability-redundant-declaration.

Author: kazutakahirata

clang-tools-extra/clang-doc/BitcodeWriter.cpp

@@ -303,8 +303,6 @@ static const std::vector<std::pair<BlockId, std::vector<RecordId>>>
 
 // AbbreviationMap
 
-constexpr unsigned char BitCodeConstants::Signature[];
-
 void ClangDocBitcodeWriter::AbbreviationMap::add(RecordId RID,
                                                  unsigned AbbrevID) {
   assert(RecordIdNameMap[RID] && "Unknown RecordId.");

clang-tools-extra/clangd/ClangdLSPServer.cpp

@@ -456,7 +456,6 @@ class ClangdLSPServer::MessageHandler : public Transport::MessageHandler {
 
   ClangdLSPServer &Server;
 };
-constexpr int ClangdLSPServer::MessageHandler::MaxReplayCallbacks;
 
 // call(), notify(), and reply() wrap the Transport, adding logging and locking.
 void ClangdLSPServer::callMethod(StringRef Method, llvm::json::Value Params,

clang-tools-extra/clangd/FileDistance.cpp

@@ -54,7 +54,6 @@ static llvm::SmallString<128> canonicalize(llvm::StringRef Path) {
   return Result;
 }
 
-constexpr const unsigned FileDistance::Unreachable;
 const llvm::hash_code FileDistance::RootHash =
     llvm::hash_value(llvm::StringRef("/"));
 

clang-tools-extra/clangd/FuzzyMatch.cpp

@@ -62,9 +62,6 @@
 namespace clang {
 namespace clangd {
 
-constexpr int FuzzyMatcher::MaxPat;
-constexpr int FuzzyMatcher::MaxWord;
-
 static char lower(char C) { return C >= 'A' && C <= 'Z' ? C + ('a' - 'A') : C; }
 // A "negative infinity" score that won't overflow.
 // We use this to mark unreachable states and forbidden solutions.

clang-tools-extra/clangd/index/SymbolLocation.cpp

@@ -11,9 +11,6 @@
 namespace clang {
 namespace clangd {
 
-constexpr uint32_t SymbolLocation::Position::MaxLine;
-constexpr uint32_t SymbolLocation::Position::MaxColumn;
-
 void SymbolLocation::Position::setLine(uint32_t L) {
   if (L > MaxLine)
     L = MaxLine;