Display library in GRASS 7

Move R_() fns to D_()

Directory lib/raster will be used for raster library. Initial step is to move R_() fns to D_() located in lib/display, see lib/raster.c​ Here is the list:

R_open_driver	D_open_driver
R_close_driver	D_close_driver
R_standard_color	D_standard_color
R_RGB_color	D_RGB_color
R_line_width	D_line_width
R_erase	D_erase
R_pos_abs	D_pos_abs
R_box_abs	D_box_abs
R_text_size	D_text_size
R_text_rotation	D_text_rotation
R_set_window	D_set_window
R_get_window	D_get_window
R_text	D_text
R_get_text_box	D_get_text_box
R_font	D_font
R_encoding	D_encoding
R_font_list	D_font_list
R_font_info	D_font_info
R_begin_scaled_raster	D_begin_scaled_raster
R_scaled_raster	D_scaled_raster
R_end_scaled_raster	D_end_scaled_raster
R_bitmap	D_bitmap
R_begin	D_begin
R_move	D_move
R_cont	D_cont
R_close	D_close
R_stroke	D_stroke
R_fill	D_fill
R_point	D_point