Add the workaround from cpradog/.ycm_extra_conf.py@aad88d

In the FAQ of Valloric/YouCompleteMe, there was an issue of C++ standard
library headers not found (ycm-core/YouCompleteMe#303) that has been
resolved with a workaround, and @cpradog has kindly implemented it.

However, this workaround has not yet been incorporated into template.py
in rdnetto/YCM-Generator, so adding this becomes the main purpose of
this fork.

template.py

@@ -30,12 +30,28 @@
 
 import os
 import ycm_core
+import re
+import subprocess
+
 
 flags = [
     # INSERT FLAGS HERE
 ]
 
 
+def LoadSystemIncludes():
+    regex = re.compile(ur'(?:\#include \<...\> search starts here\:)(?P<list>.*?)(?:End of search list)', re.DOTALL);
+    process = subprocess.Popen(['clang', '-v', '-E', '-x', 'c++', '-'], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE);
+    process_out, process_err = process.communicate('');
+    output = process_out + process_err;
+    includes = [];
+    for p in re.search(regex, output).group('list').split('\n'):
+        p = p.strip();
+        if len(p) > 0 and p.find('(framework directory)') < 0:
+            includes.append('-isystem');
+            includes.append(p);
+    return includes;
+
 # Set this to the absolute path to the folder (NOT the file!) containing the
 # compile_commands.json file to use that instead of 'flags'. See here for
 # more details: http://clang.llvm.org/docs/JSONCompilationDatabase.html
@@ -54,6 +70,8 @@
   database = None
 
 SOURCE_EXTENSIONS = [ '.C', '.cpp', '.cxx', '.cc', '.c', '.m', '.mm' ]
+systemIncludes = LoadSystemIncludes();
+flags = flags + systemIncludes;
 
 def DirectoryOfThisScript():
   return os.path.dirname( os.path.abspath( __file__ ) )
@@ -121,7 +139,7 @@ def FlagsForFile( filename, **kwargs ):
 
     final_flags = MakeRelativePathsInFlagsAbsolute(
       compilation_info.compiler_flags_,
-      compilation_info.compiler_working_dir_ )
+      compilation_info.compiler_working_dir_ ) + systemIncludes 
 
   else:
     relative_to = DirectoryOfThisScript()