In keymap_poker.c :

#include "keymap_common.h"

const uint8_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
           KEYMAP(ESC,KC_KP_SLASH,KC_KP_ASTERISK,KC_KP_MINUS, \
           KC_KP_7,KC_KP_8,KC_KP_9, \
           KC_KP_4,KC_KP_5,KC_KP_6,KC_KP_PLUS, \
           KC_KP_1,KC_KP_2,KC_KP_3, \
           KC_KP_ENTER,KC_KP_DOT,KC_KP_0)
};

const uint16_t PROGMEM fn_actions[] = {

};

---------------------
In keymap_common.h (fixed comma) :

extern const uint8_t keymaps[][MATRIX_ROWS][MATRIX_COLS];
//extern const uint16_t fn_actions[];


/* GH60 keymap definition macro
 * K2C, K31 and  K3C are extra keys for ISO
 */
#define KEYMAP( \
    K00, K01, K02, K03, \
    K10, K11, K12, \
    K20, K21, K22, K23, \
    K30, K31, K32, \
    K40, K41, K42, \
) { \
    { KC_##K00, KC_##K01, KC_##K02, KC_##K03 }, \
    { KC_##K10, KC_##K11, KC_##K12, KC_NO}, \
    { KC_##K20, KC_##K21, KC_##K22, KC_##K23 }, \
    { KC_##K30, KC_##K31, KC_##K32, KC_NO }, \
    { KC_##K40, KC_NO, KC_##K41, KC_##K42}  \
}
#endif

--------------------------
In config.h :
/* key matrix size */
#define MATRIX_ROWS 5
#define MATRIX_COLS 4
 -------------------------
In config.h :

/* Column pin configuration
 * col: 0   1   2   3
 * pin: F4  F1  F5  F6
*/
static void  init_cols(void)
{
        DDRF &= ~(1<<4 | 1<<1 | 1<<5 | 1<<6);
        PORTF |= (1<<4 | 1<<1 | 1<<5 | 1<<6);
    // Input with pull-up(DDR:0, PORT:1)
}

static matrix_row_t read_cols(void)
{
        return (PINF&(1<<4) ? 0 : (1<<0)) |
                   (PINF&(1<<1) ? 0 : (1<<1)) |
                   (PINF&(1<<5) ? 0 : (1<<2)) |
                   (PINF&(1<<6) ? 0 : (1<<3));
}

/* Row pin configuration
 * row: 0   1   2   3   4
 * pin: B1  B2  B3  B7  B0
 */
static void unselect_rows(void)
{
    // Hi-Z(DDR:0, PORT:0) to unselect
    DDRB  &= ~0b10001111;
    PORTB &= ~0b00001111;
}

static void select_row(uint8_t row)
{
    // Output low(DDR:1, PORT:0) to select
    switch (row) {
        case 0:
            DDRB  |= (1<<1);
            PORTB &= ~(1<<1);
            break;
        case 1:
            DDRB  |= (1<<2);
            PORTB &= ~(1<<2);
            break;
        case 2:
            DDRB  |= (1<<3);
            PORTB &= ~(1<<3);
            break;
        case 3:
            DDRB  |= (1<<7);
            PORTB &= ~(1<<7);
            break;
        case 4:
            DDRB  |= (1<<0);
            PORTB &= ~(1<<0);
            break;
    }
}
--------------------------
Error from cygwin64:

mkdir -p obj_gh60_lufa
Compiling C: keymap_poker.c
avr-gcc -c -mmcu=atmega32u4 -gdwarf-2 -DF_CPU=16000000UL -DINTERRUPT_CONTROL_ENDPOINT -DBOOTLOADER_SIZE=4096 -DF_USB=16000000UL -DARCH=ARCH_AVR8 -DUSB_DEVICE_ONLY -DUSE_FLASH_DESCRIPTORS -DUSE_STATIC_OPTIONS="(USB_DEVICE_OPT_FULLSPEED | USB_OPT_REG_ENABLED | USB_OPT_AUTO_PLL)" -DFIXED_CONTROL_ENDPOINT_SIZE=8  -DFIXED_NUM_CONFIGURATIONS=1 -DPROTOCOL_LUFA -DBOOTMAGIC_ENABLE -DMOUSEKEY_ENABLE -DMOUSE_ENABLE -DEXTRAKEY_ENABLE -DCONSOLE_ENABLE -DCOMMAND_ENABLE -DNKRO_ENABLE -DVERSION=unknown -Os -funsigned-char -funsigned-bitfields -ffunction-sections -fno-inline-small-functions -fpack-struct -fshort-enums -fno-strict-aliasing -Wall -Wstrict-prototypes -Wa,-adhlns=obj_gh60_lufa/keymap_poker.lst -I. -I../.. -I../../protocol/lufa -I../../protocol/lufa/LUFA-120730 -I../../common -std=gnu99 -include config.h -MMD -MP -MF .dep/obj_gh60_lufa_keymap_poker.o.d  keymap_poker.c -o obj_gh60_lufa/keymap_poker.o
In file included from keymap_poker.c:1:0:
keymap_common.h:46:1: error: parameter name missing
 ) { \
 ^
keymap_poker.c:4:6: warning: implicit declaration of function 'KEYMAP' [-Wimplicit-function-declaration]
      KEYMAP(ESC,KC_KP_SLASH,KC_KP_ASTERISK,KC_KP_MINUS, \
      ^
keymap_poker.c:4:13: error: 'ESC' undeclared here (not in a function)
      KEYMAP(ESC,KC_KP_SLASH,KC_KP_ASTERISK,KC_KP_MINUS, \
             ^
../../rules.mk:541: recipe for target 'obj_gh60_lufa/keymap_poker.o' failed
make: *** [obj_gh60_lufa/keymap_poker.o] Error 1