Update InstallationGuide

InstallationGuide

@@ -39,7 +39,7 @@
       However, this is your choice, but the GOPATH environment variable must be set :
 
    - set the env variable accordingly depending on your OS
-        e.g. export GOPATH=*go*  on MacOS, set GOPATH=*go* on Windows, etc
+        e.g. export GOPATH=*go*  on MacOS or Linux, set GOPATH=*go* on Windows, etc
 
    - On recent go versions, you need to set the GO111MODULE variable 
        export GO111MODULE=off
@@ -49,6 +49,9 @@
         - the claire4.go file
         - all the subdirectories and their contents: Kernel, Core, Language, Reader, Optimize, Generate
 
+    - set the CLAIRE_HOME variable
+        export CLAIRE_HOME=*go*/src
+
     - build the claire4 executable:
         go build src/claire4.go
 
@@ -60,7 +63,7 @@
      If an init.cl file is present, it will be loaded first
      modules are defined in the init file (think of it as a configuration file)
 
-   - claire3 -cm <module> will compile a module into an executable
+   - claire4 -cm <module> will compile a module into an executable
 
 
    (4) Playing with the demo performance tests 
@@ -76,6 +79,9 @@
    - claire4 -cc <M> will compile a module M and place the generated go code under src/<M>
    - claire4 -sf <M> -o <name>  creates a "system file" that will include M and all its dependencies
    - go build src/<name>  will create an executable : this is how claire4 was built :)
+
+    You need to update the init.cl file (either from the root version, or you may find some simpler and OS-optimized 
+    versions in the interpreter subdirectories