In keymap_common.h :

#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 keymap_poker.h :

#include "keymap_common.h"

const uint8_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
           KEYMAP(KC_ESCAPE,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[] = {

};

----------------------
Full 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(KC_ESCAPE,KC_KP_SLASH,KC_KP_ASTERISK,KC_KP_MINUS, \
      ^
keymap_poker.c:4:6: warning: missing braces around initializer [-Wmissing-braces]
keymap_poker.c:4:6: warning: (near initialization for 'keymaps[0]') [-Wmissing-braces]
keymap_poker.c:4:6: error: initializer element is not constant
keymap_poker.c:4:6: error: (near initialization for 'keymaps[0][0][0]')
../../rules.mk:541: recipe for target 'obj_gh60_lufa/keymap_poker.o' failed
make: *** [obj_gh60_lufa/keymap_poker.o] Error 1