sal: (win32) readd comment explaining about buffer size decision

Readd comment explaining why we allocate a large buffer for
GetEnvironmentVariableW which was removed in commit
f78a2bcc:

    re-base on ALv2 code. Includes:
        Patch contributed by Herbert Duerr:
        #i118662# remove berkeleyDB from module xmlhelp (author=orwitt)
        http://svn.apache.org/viewvc?view=revision&revision=1213188
        #i119141# remove ISCII converter for now
        http://svn.apache.org/viewvc?view=revision&revision=1306246
        make exceptions for cppunittester verbose
        http://svn.apache.org/viewvc?view=revision&revision=1174831

        Patches contributed by Pedro Giffuni:
        Avoid some uses of non portable #!/bin/bash in shell scripts.
        http://svn.apache.org/viewvc?view=revision&revision=1235297

        Patch contributed by Oliver-Rainer Wittmann
        88652: applied patch, remove unicows deps
        http://svn.apache.org/viewvc?view=revision&revision=1177585

    drop OS/2 code, remove in-line assembler ARM atomics,
    and obsolete armarch header.

Change-Id: I75a222393e202e40d78f10fc97f5eb4aad2df743
Reviewed-on: https://gerrit.libreoffice.org/47018Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

sal/osl/w32/process.cxx

@@ -440,6 +440,11 @@ void SAL_CALL osl_setCommandArgs (int argc, char ** argv)
     osl_releaseMutex (*osl_getGlobalMutex());
 }
 
+/* TODO because of an issue with GetEnvironmentVariableW we have to
+   allocate a buffer large enough to hold the requested environment
+   variable instead of testing for the required size. This wastes
+   some stack space, maybe we should revoke this work around if
+   this is no longer a problem */
 #define ENV_BUFFER_SIZE (32*1024-1)
 
 oslProcessError SAL_CALL osl_getEnvironment(rtl_uString *ustrVar, rtl_uString **ustrValue)