Move scmxlated source for slatex into private.

Anyone using the sole export from slatex.rkt should really be using the
functions provided by slatex-wrapper.rkt instead, which I imagine is why
this has never been documented.

collects/slatex/README

@@ -12,8 +12,8 @@ this involves downloading the 'scmxlate' and 'slatex' packages and loading
 the scmxlate.scm file while (current-directory) points to the slatex 
 directory.
 
-2) place this file in plt/collects/slatex (this directory).
-3) also copy slatex.sty to plt/collects/slatex.
+2) place this file in $PLTHOME/collects/slatex/private.
+3) also copy slatex.sty to $PLTHOME/collects/slatex.
 
 4) (hopefully temporary?) Modify slatex.scm so that it doesn't refer to
    slatex::slatex-error at evaluation time.

collects/slatex/slatex-wrapper.rkt

@@ -5,7 +5,7 @@
 	   mzlib/process
 	   mzlib/sendevent
            scheme/runtime-path
-           "slatex.ss")
+           "private/slatex.ss")
   
   (define-runtime-path here ".")
 

collects/slatex/tests/test-docs-complete.rkt

@@ -1,6 +1,5 @@
 #lang racket/base
 (require tests/utils/docs-complete)
-(check-docs (quote slatex/slatex))
 (check-docs (quote slatex/slatex-wrapper))
 (check-docs (quote slatex/slatex-launcher))
 (check-docs (quote slatex/pdf-slatex-launcher))