'nimcache' defaults to ~/.cache on Posix; cleaned up documentation

doc/backends.txt

@@ -65,7 +65,6 @@ The JavaScript target
 ---------------------
 
 Nim can also generate `JavaScript`:idx: code through the ``js`` command.
-However, the JavaScript code generator is experimental!
 
 Nim targets JavaScript 1.5 which is supported by any widely used browser.
 Since JavaScript does not have a portable means to include another module,
@@ -77,7 +76,7 @@ available. This includes:
 * manual memory management (``alloc``, etc.)
 * casting and other unsafe operations (``cast`` operator, ``zeroMem``, etc.)
 * file management
-* most modules of the Standard library
+* most modules of the standard library
 * proper 64 bit integer arithmetic
 * unsigned integer arithmetic
 
@@ -87,9 +86,8 @@ However, the modules `strutils <strutils.html>`_, `math <math.html>`_, and
 
 To compile a Nim module into a ``.js`` file use the ``js`` command; the
 default is a ``.js`` file that is supposed to be referenced in an ``.html``
-file. However, you can also run the code with `nodejs`:idx:, a `software
-platform for easily building fast, scalable network applications
-<http://nodejs.org>`_::
+file. However, you can also run the code with `nodejs`:idx:
+(`<http://nodejs.org>`_)::
 
   nim js -d:nodejs -r examples/hallo.nim
 
@@ -330,8 +328,9 @@ Nimcache naming logic
 
 The `nimcache`:idx: directory is generated during compilation and will hold
 either temporary or final files depending on your backend target. The default
-name for the directory is ``nimcache`` but you can use the ``--nimcache``
-`compiler switch <nimc.html#command-line-switches>`_ to change it.
+name for the directory depends on the used backend and on your OS but you can
+use the ``--nimcache`` `compiler switch <nimc.html#command-line-switches>`_ to
+change it.
 
 Nimcache and C like targets
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~