add GLEW to build dependencies in cmake and doc

Author: q4a

CMakeLists.txt

@@ -45,6 +45,7 @@ if(EXISTS ${CMAKE_SOURCE_DIR}/Externals/cryptopp/dsa.h)
     file(REMOVE_RECURSE ${CMAKE_SOURCE_DIR}/Externals/cryptopp)
     file(MAKE_DIRECTORY ${CMAKE_SOURCE_DIR}/Externals/cryptopp)
 endif()
+find_package(GLEW REQUIRED)
 find_package(FreeImage REQUIRED)
 find_package(LockFile REQUIRED)
 find_package(OpenAL REQUIRED)

doc/howto/build-linux.txt

@@ -2,6 +2,7 @@ TITLE: X-Ray 1.6 build and setup on Linux
 
 Required packages:
 ------
+GLEW
 FreeImage
 LockFile
 OpenAL
@@ -16,7 +17,7 @@ JPEG
 
 
 Ubuntu 18.04 build dependencies:
-sudo apt install git cmake libfreeimage-dev liblockfile-dev libopenal-dev libtbb-dev libcrypto++-dev libpugixml-dev libogg-dev libtheora-dev libvorbis-dev libsdl2-dev liblzo2-dev libjpeg-dev libncurses5-dev libreadline-dev
+sudo apt install git cmake libglew-dev libfreeimage-dev liblockfile-dev libopenal-dev libtbb-dev libcrypto++-dev libpugixml-dev libogg-dev libtheora-dev libvorbis-dev libsdl2-dev liblzo2-dev libjpeg-dev libncurses5-dev libreadline-dev
 
 Build commands:
 ------