Rename custom error from Sass_Error to Error_Invalid

Avoids name-clash with C-API `Sass_Error` value type!

Author: mgreter

error_handling.cpp

@@ -4,7 +4,7 @@
 
 namespace Sass {
 
-  Sass_Error::Sass_Error(Type type, ParserState pstate, string message)
+  Error_Invalid::Error_Invalid(Type type, ParserState pstate, string message)
   : type(type), pstate(pstate), message(message)
   { }
 
@@ -31,7 +31,7 @@ namespace Sass {
 
   void error(string msg, ParserState pstate)
   {
-    throw Sass_Error(Sass_Error::syntax, pstate, msg);
+    throw Error_Invalid(Error_Invalid::syntax, pstate, msg);
   }
 
   void error(string msg, ParserState pstate, Backtrace* bt)

error_handling.hpp

@@ -10,14 +10,14 @@ namespace Sass {
 
   struct Backtrace;
 
-  struct Sass_Error {
+  struct Error_Invalid {
     enum Type { read, write, syntax, evaluation };
 
     Type type;
     ParserState pstate;
     string message;
 
-    Sass_Error(Type type, ParserState pstate, string message);
+    Error_Invalid(Type type, ParserState pstate, string message);
 
   };
 

parser.cpp

@@ -2398,7 +2398,7 @@ namespace Sass {
 
   void Parser::error(string msg, Position pos)
   {
-    throw Sass_Error(Sass_Error::syntax, ParserState(path, source, pos.line ? pos : before_token, Offset(0, 0)), msg);
+    throw Error_Invalid(Error_Invalid::syntax, ParserState(path, source, pos.line ? pos : before_token, Offset(0, 0)), msg);
   }
 
   // print a css parsing error with actual context information from parsed source

sass_context.cpp

@@ -221,7 +221,7 @@ extern "C" {
     try {
      throw;
     }
-    catch (Sass_Error& e) {
+    catch (Error_Invalid& e) {
       stringstream msg_stream;
       string cwd(Sass::File::get_cwd());
       JsonNode* json_err = json_mkobject();

sass_interface.cpp

@@ -143,7 +143,7 @@ extern "C" {
 
       copy_strings(cpp_ctx.get_included_files(1), &c_ctx->included_files, 1);
     }
-    catch (Sass_Error& e) {
+    catch (Error_Invalid& e) {
       stringstream msg_stream;
       msg_stream << e.pstate.path << ":" << e.pstate.line << ": " << e.message << endl;
       c_ctx->error_message = sass_strdup(msg_stream.str().c_str());
@@ -235,7 +235,7 @@ extern "C" {
 
       copy_strings(cpp_ctx.get_included_files(), &c_ctx->included_files);
     }
-    catch (Sass_Error& e) {
+    catch (Error_Invalid& e) {
       stringstream msg_stream;
       msg_stream << e.pstate.path << ":" << e.pstate.line << ": " << e.message << endl;
       c_ctx->error_message = sass_strdup(msg_stream.str().c_str());