For finding svgalib functions used.

Lists of libvga and libvgag found in libvga_symbols.txt and
libvgagl_symbols.txt, generated with:
nm -D --defined-only /usr/lib/libvga.so.1.4.3 > libvga_symbols.txt
nm -D --defined-only /usr/lib/libvgagl.so.1.4.3 > libvgagl_symbols.txt

To find used functions in zblast:
$ for i in `cat libvga_symbols.txt`; do [ $i != "D" -a $i != "T" -a $i != "A" -a $i != "B" -a $i != "R" ] && grep -w -F -o -I "$i" /home/cmp/svgalib/zblast-1.3/*; done | sort -u
/home/cmp/svgalib/zblast-1.3/font.c:vga_drawline
/home/cmp/svgalib/zblast-1.3/font.c:vga_drawpixel
/home/cmp/svgalib/zblast-1.3/zblast.c:keyboard_close
/home/cmp/svgalib/zblast-1.3/zblast.c:keyboard_getstate
/home/cmp/svgalib/zblast-1.3/zblast.c:keyboard_init
/home/cmp/svgalib/zblast-1.3/zblast.c:keyboard_keypressed
/home/cmp/svgalib/zblast-1.3/zblast.c:keyboard_translatekeys
/home/cmp/svgalib/zblast-1.3/zblast.c:keyboard_update
/home/cmp/svgalib/zblast-1.3/zblast.c:vga_disabledriverreport
/home/cmp/svgalib/zblast-1.3/zblast.c:vga_drawline
/home/cmp/svgalib/zblast-1.3/zblast.c:vga_drawpixel
/home/cmp/svgalib/zblast-1.3/zblast.c:vga_hasmode
/home/cmp/svgalib/zblast-1.3/zblast.c:vga_init
/home/cmp/svgalib/zblast-1.3/zblast.c:vga_setcolor
/home/cmp/svgalib/zblast-1.3/zblast.c:vga_setmode
vga_drawline

$ for i in `cat libvgagl_symbols.txt`; do [ $i != "D" -a $i != "T" -a $i != "A" -a $i != "B" -a $i != "R" ] && grep -w -F -o -I "$i" /home/cmp/svgalib/zblast-1.3/*; done | sort -u
/home/cmp/svgalib/zblast-1.3/font.c:gl_line
/home/cmp/svgalib/zblast-1.3/font.c:gl_setpixel
/home/cmp/svgalib/zblast-1.3/zblast.c:currentcontext
/home/cmp/svgalib/zblast-1.3/zblast.c:gl_clearscreen
/home/cmp/svgalib/zblast-1.3/zblast.c:gl_copyscreen
/home/cmp/svgalib/zblast-1.3/zblast.c:gl_enableclipping
/home/cmp/svgalib/zblast-1.3/zblast.c:gl_line
/home/cmp/svgalib/zblast-1.3/zblast.c:gl_setcontextvga
/home/cmp/svgalib/zblast-1.3/zblast.c:gl_setcontextvgavirtual
/home/cmp/svgalib/zblast-1.3/zblast.c:gl_setpalettecolor
/home/cmp/svgalib/zblast-1.3/zblast.c:gl_setpixel

Add "-h" to grep command to list/show only the unique function names:
$ for i in `cat libvga_symbols.txt`; do [ $i != "D" -a $i != "T" -a $i != "A" -a $i != "B" -a $i != "R" ] && grep -w -F -o -I -h "$i" /home/cmp/svgalib/zblast-1.3/*; done | sort -u
keyboard_close
keyboard_getstate
keyboard_init
keyboard_keypressed
keyboard_translatekeys
keyboard_update
vga_disabledriverreport
vga_drawline
vga_drawpixel
vga_hasmode
vga_init
vga_setcolor
vga_setmode

$ for i in `cat libvgagl_symbols.txt`; do [ $i != "D" -a $i != "T" -a $i != "A" -a $i != "B" -a $i != "R" ] && grep -w -F -o -I -r -h "$i" /home/cmp/svgalib/zblast-1.3/*; done | sort -u
currentcontext
gl_clearscreen
gl_copyscreen
gl_enableclipping
gl_line
gl_setcontextvga
gl_setcontextvgavirtual
gl_setpalettecolor
gl_setpixel