Update build settings to current Xcode recomendation

Lib/Configurations/Base.xcconfig

@@ -1,6 +1,7 @@
 ALWAYS_SEARCH_USER_PATHS = NO;
+CLANG_ANALYZER_NONNULL = YES
 CLANG_CXX_LANGUAGE_STANDARD = gnu++0x;
-CLANG_CXX_LIBRARY = "libc++";
+CLANG_CXX_LIBRARY = libc++;
 CLANG_ENABLE_MODULES = YES;
 CLANG_ENABLE_OBJC_ARC = YES;
 CLANG_WARN_BOOL_CONVERSION = YES;
@@ -15,6 +16,7 @@ CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 CURRENT_PROJECT_VERSION = 1;
 ENABLE_STRICT_OBJC_MSGSEND = YES;
 GCC_C_LANGUAGE_STANDARD = gnu99;
+GCC_NO_COMMON_BLOCKS = YES
 GCC_DYNAMIC_NO_PIC = NO;
 GCC_SYMBOLS_PRIVATE_EXTERN = NO;
 GCC_WARN_64_TO_32_BIT_CONVERSION = YES;