Update installation guides with CMake 3.8 requirement

Change-Id: I4d77a913d13c9840c4471371ed37fb402710d6c1

doc/installation.md

@@ -31,14 +31,18 @@ The scripts and commands below invoke `wget, git, add-apt-repository` which may
     `sudo apt-get install git libssl-dev libusb-1.0-0-dev pkg-config libgtk-3-dev`  <br /><br />
     Distribution-specific packages:  <br />
      * Ubuntu 14 or when running of Ubuntu 16.04 live-disk:<br />
-      `sudo apt-get install cmake3`<br />
+      `sudo apt-get install`<br />
       `./scripts/install_glfw3.sh`  <br />
 
      * Ubuntu 16:<br />
-      `sudo apt-get install cmake3 libglfw3-dev`<br />
+      `sudo apt-get install libglfw3-dev`<br />
 
      * Ubuntu 18:<br />
-      `sudo apt-get install cmake libglfw3-dev libgl1-mesa-dev libglu1-mesa-dev`  <br /><br />
+      `sudo apt-get install libglfw3-dev libgl1-mesa-dev libglu1-mesa-dev`  <br /><br />
+
+    Cmake: *librealsense* requires version 3.8+ which is currently not made available via apt manager for Ubuntu LTS.   
+    Go to the [official CMake site](https://cmake.org/download/) to download and install the application  
+
 
      **Note** on graphic sub-system utilization:<br />
      *glfw3*, *mesa* and *gtk* packages are required if you plan to build the SDK's OpenGl-enabled examples. The *librealsense* core library and a range of demos/tools are designed for headless environment deployment.
@@ -69,7 +73,7 @@ The scripts and commands below invoke `wget, git, add-apt-repository` which may
 
       `./scripts/patch-realsense-ubuntu-odroid.sh`<br />
       Some additional details on the Odroid installation can also be found in [installation_odroid.md](installation_odroid.md)
-      
+
     * Check the patched modules installation by examining the generated log as well as inspecting the latest entries in kernel log:<br />
       `sudo dmesg | tail -n 50`<br />
     The log should indicate that a new uvcvideo driver has been registered.  

doc/installation_osx.md

@@ -1,6 +1,6 @@
 # macOS Installation  
 
-**Note:** macOS support for the full range of functionality offered by the SDK is not yet complete. If you need support for R200 or the ZR300, [legacy librealsense](https://github.com/IntelRealSense/librealsense/tree/legacy) offers a subset of SDK functionality. 
+**Note:** macOS support for the full range of functionality offered by the SDK is not yet complete. If you need support for R200 or the ZR300, [legacy librealsense](https://github.com/IntelRealSense/librealsense/tree/legacy) offers a subset of SDK functionality.
 
 ## Building from Source
 
@@ -10,6 +10,10 @@
   * `brew install libusb pkg-config`
   * `brew install homebrew/core/glfw3`
   * `brew install cmake`
+
+**Note** *librealsense* requires CMake version 3.8+ that can be obtained via the [official CMake site](https://cmake.org/download/).  
+
+
 4. Generate XCode project:
   * `mkdir build && cd build`
   * `sudo xcode-select --reset`

doc/installation_windows.md

@@ -2,7 +2,7 @@
 
 **Note:** Due to the USB 3.0 translation layer between native hardware and virtual machine, the librealsense team does not recommend or support installation in a VM.
 
-librealsense shall be built on Windows using [CMake](https://cmake.org/download/) and Visual Studio 2015 / 2017:  
+librealsense shall be built on Windows using [CMake v3.8+](https://cmake.org/download/) and Visual Studio 2015 / 2017:  
 (MSVC2013 and older are not fully compatible with the C++11 feature-set).
 <a name="cmake_snapshot_win">
    ![Windows CMake](./img/windows_cmake.png)