Add some readme stuff from the master branch

README.md

@@ -6,10 +6,19 @@ This branch migrates the engine from WinAPI to SDL2, and addresses numerous port
 
 ![Screenshot](screenshot.png)
 
+## Dependencies
+
+* SDL2
+* FLTK
+* GLEW (if the OpenGL rendering backend is selected)
+
+
 ## Building
 
 ### Makefile
 
+*Note: this requires pkg-config*
+
 Run 'make' in this folder, preferably with some of the following settings:
 
 * `RELEASE=1` - Compile a release build (optimised, stripped, etc.)
@@ -17,6 +26,10 @@ Run 'make' in this folder, preferably with some of the following settings:
 * `JAPANESE=1` - Enable the Japanese-language build (instead of the unofficial Aeon Genesis English translation)
 * `FIX_BUGS=1` - Fix bugs in the game (see [src/Bug Fixes.txt](src/Bug%20Fixes.txt))
 * `DEBUG_SAVE=1` - Re-enable the ability to drag-and-drop save files onto the window
+* `RENDERER=OpenGL3` - Use the hardware-accelerated OpenGL 3.2 renderer
+* `RENDERER=Texture` - Use the hardware-accelerated SDL2 Texture API renderer (default)
+* `RENDERER=Surface` - Use the software-rendered SDL2 Surface API renderer
+* `RENDERER=Software` - Use a hand-written software renderer
 
 ## Licensing