bug#18122: make error when configure --without-x

[Dmitry Antipov]

Moreover, it's just broken with --enable-gcc-warnings:

../../trunk/src/frame.c:371:1: error: no previous prototype for 
‘frame_windows_min_size’ [-Werror=missing-prototypes]
 frame_windows_min_size (Lisp_Object frame, Lisp_Object horizontal, Lisp_Object 
pixelwise)
 ^
../../trunk/src/frame.c:413:1: error: no previous prototype for 
‘adjust_frame_size’ [-Werror=missing-prototypes]
 adjust_frame_size (struct frame *f, int new_width, int new_height, int 
inhibit, bool pretend)
 ^
../../trunk/src/frame.c: In function ‘adjust_frame_size’:
../../trunk/src/frame.c:479:9: error: implicit declaration of function 
‘FRAME_HAS_HORIZONTAL_SCROLL_BARS’ [-Werror=implicit-function-declaration]
         : max (FRAME_TEXT_TO_PIXEL_HEIGHT (f, new_text_height),
         ^
cc1: all warnings being treated as errors

And:

../../trunk/src/dispnew.c: In function ‘change_frame_size_1’:
../../trunk/src/dispnew.c:5509:7: error: implicit declaration of function 
‘adjust_frame_size’ [-Werror=implicit-function-declaration]
       adjust_frame_size (f, new_width, new_height, 5, pretend);
       ^
cc1: all warnings being treated as errors

GCC 4.8.3.

Dmitry