I find a bunch of underlined "errors" which actually compile fine.

e.g. in 

#include <avr/eeprom.h>
#define eeprom_read_to(dst_p, eeprom_field, dst_size) eeprom_read_block(dst_p, (void *)offsetof(__eeprom_data, eeprom_field), MIN(dst_size, sizeof((__eeprom_data*)0)->eeprom_field))
struct __eeprom_data {
    uint16_t magic;
    uint16_t version;
};

void setup()
{
    uint16_t magic;
    uint16_t version;
    eeprom_read(magic, magic);
    eeprom_read(version, version);
}


Also, 

FastSerialPort(Serial,0);
...
Serial.print(F("!IYMO Config found\r\n"));
Serial.printf_P(F("!Version %04X\r\n"), version);

Squiggles disappeared, reappeared, a few times... then I noticed the status line said 13 of 100.  A couple of minutes later, all the libraries are showing in the project.

eeprom_read is now good, eeprom_write still underlined. (These are similar and located in same header).

Serial.print(F("Something")) is good in some places but not others, 
Serial.printf_P(F("Something %ld"), myLong) is not.

I'm using VS2012.