Add GLEW information to the Linux and MacOSX readme files.

README.Linux

@@ -30,12 +30,12 @@ BZFlag.  Known build requirements include:
 
     apt-get install g++ libtool automake autoconf libgl1-mesa-dev \
     libglu1-mesa-dev libsdl1.2-dev libsdl-sound1.2-dev libcurl3-dev \
-    libc-ares-dev zlib1g-dev libncurses-dev make
+    libc-ares-dev zlib1g-dev libncurses-dev libglew-dev make
 
   Fedora:
 
     yum install SDL-devel c-ares-devel libSM-devel libcurl-devel \
-    gcc-c++ libidn-devel libtool ncurses-devel zlib-devel
+    gcc-c++ libidn-devel libtool ncurses-devel zlib-devel glew-devel
 
 After any development packages are installed, execute the following
 commands from the top-level BZFlag source directory:

README.MacOSX

@@ -50,7 +50,7 @@ additionally be able to build using the traditional autotools method. See the
 README file for further information. You will still need to install the SDL 2
 framework as detailed below.
 
-BZFlag has two external dependencies: SDL 2 and c-ares.
+BZFlag has three external dependencies: SDL 2, GLEW, and c-ares.
 
 Download the latest version of the SDL 2 framework from
 https://www.libsdl.org/download-2.0.php. Version 2.0.3 or later is required,
@@ -63,9 +63,22 @@ obtained a binary release of SDL 2, mount the disk image and place the file
 account may be required). If you built SDL 2 from source, locate the file
 "SDL2.framework" and copy it into that same location.
 
-This project expects the c-ares library and header files to be located in
-/usr/local. If you install it elsewhere, you must update the library and
-header search paths in this project file appropriately.
+This project expects the GLEW and c-ares libraries and header files to be
+located in /usr/local. If you install them elsewhere, you must update the
+library and header search paths in this project file appropriately.
+
+Download the latest version of GLEW from
+https://github.com/nigels-com/glew/releases. Extract the package, and then
+build it with the following commands (WARNING: this will remove all shared
+libraries for GLEW under /usr/local, even older versions you may have
+installed; this is necessary because it appears there is currently no way to
+configure GLEW to build without shared libraries):
+
+$ export MACOSX_DEPLOYMENT_TARGET=10.7
+$ export GLEW_DEST=/usr/local
+$ make glew.lib
+$ sudo make install
+$ sudo rm /usr/local/lib/libGLEW*.dylib
 
 Download the latest version of c-ares from http://c-ares.haxx.se.
 Extract the package, and then build it with the following commands: