Proposal: Close sessions with regards to multiple callers

This proposal adds clarifications to C_CloseSession and C_CloseAllSessions noting their raciness with regard to login state, if multiple callers of a PKCS#11 token are present within a process.
In addition it adds warnings about when it is appropriate to use C_CloseAllSessions.
Cheers, Stef 11.6 Session management functions *** Remove last clause of paragraph 5.
Call C_CloseSession once for each session that the application has with the token.
o C_CloseSession *** Add paragraph Applications should be aware that another caller of the token within the same process (such as within a shared library) may have a session open with the token, or may open one during or after the call to C_CloseSession.
*** Add paragraph Unless the application can guarantee that it is aware of all sessions, it cannot make assumptions about the login state of the token after a C_CloseSession call.
o C_CloseAllSessions *** Add paragraph Applications should be aware that another caller of the token within the same process (such as within a shared library) may have a session open with the token, or may open one during or after the call to C_CloseAllSessions.
*** Add paragraph Unless the application can guarantee that it is aware of all sessions, it cannot make assumptions about the login state of the token after a C_CloseAllSessions call.
*** Add paragraph Because other callers within the same process may be using other sessions unbeknownst to the caller, this function should only be called in response to a user action or other significant event.