Moved documentation to docs, recreated a simple README.txt, fixed build

INSTALL.txt

@@ -9,7 +9,7 @@ To compile and install SDL:
         * Run './configure; make; make install'
 
         Mac OS X with Xcode:
-        * Read README-macosx.txt
+        * Read docs/README-macosx.md
 
         Mac OS X from the command line:
         * Run './configure; make; make install'
@@ -18,13 +18,13 @@ To compile and install SDL:
         * Run './configure; make; make install'
 
         Android:
-        * Read README-android.txt
+        * Read docs/README-android.md
 
         iOS:
-        * Read README-ios.txt
+        * Read docs/README-ios.md
 
         Using Cmake:
-        * Read README-cmake.txt
+        * Read docs/README-cmake.md
 
     2.  Look at the example programs in ./test, and check out the online
         documentation at http://wiki.libsdl.org/

README.txt

@@ -0,0 +1,21 @@
+
+                         Simple DirectMedia Layer
+
+                                  (SDL)
+
+                                Version 2.0
+
+---
+http://www.libsdl.org/
+
+Simple DirectMedia Layer is a cross-platform development library designed
+to provide low level access to audio, keyboard, mouse, joystick, and graphics
+hardware via OpenGL and Direct3D. It is used by video playback software,
+emulators, and popular games including Valve's award winning catalog
+and many Humble Bundle games.
+
+More extensive documentation is available in the docs directory, starting
+with README.md
+
+Enjoy!
+	Sam Lantinga				(slouken@libsdl.org)