fixed typo

git-svn-id: svn+ssh://svn.berlios.de/svnroot/repos/slim/trunk@148 7c53e7cc-98ea-0310-8f1f-a0b24da60408

INSTALL

@@ -9,7 +9,7 @@ INSTALL file for SLiM
  - edit the Makefile to adjust libraries and paths to your OS (if needed)
  - make
      or
- - make ENABLE_PAM=1 to enable PAM support 
+ - make USE_PAM=1 to enable PAM support 
  - make install
  
 Pre-configured makefiles for some platform are available,