Update INSTALL file

INSTALL

@@ -1,20 +1,27 @@
 WeeChat - Installation instructions
 ===================================
 
-You can build WeeChat with autotools or cmake.
-
-- with autotools:
-    ./autogen.sh     (for cloned git repository only)
-    ./configure      ("./configure --help" for options)
-    make
-    make install     (as root for installation in system directories)
+You can build WeeChat with cmake (recommended way) or autotools.
 
 - with cmake:
+
     mkdir build
     cd build
-    cmake ..         ("ccmake .." for options)
+    cmake .. -DPREFIX=/where/you/want/install -DCMAKE_BUILD_TYPE=Debug
     make
     make install     (as root for installation in system directories)
 
+- with autotools:
+
+    ./autogen.sh     (for cloned git repository only, not devel package)
+    ./configure --prefix=/where/you/want/install
+    make
+    make install     (as root for installation in system directories)
+
+
+If you want to report bugs/crashs to developers, please:
+- compile with debug info (built type Debug for cmake, default for autotools),
+- enable core files (for bash shell, add "ulimit -c unlimited" to your ~/.bashrc).
+
 
 See AUTHORS for support, feel free to contact us for any problem.