add simple .library syntax

[Stan Cox <scox at redhat dot com>]

This patch adds a simple implementation of .library("library") to
assist the task finder so that an external variable can be found in a
shared object.  This is bug 6880.  It adds .library to uprobe and utrace 
probes so that process("process").library("library").mark("mark") can be 
converted to either a uprobe or utrace probe.  The .library support is 
currently simple since  LD_LIBRARY_PATH is not searched.  emit_module_decls in 
both utrace_derived_probe_group and uprobe_derived_probe_group add
machinery to access and set a static user probe semaphore, which is
actually an external variable.  The writeable portion of a shared
object will be mapped into a separate segment, so when the task finder
notices this then the value is accessed via _access_process_vm and incremented.

Attachment: ,git.diff
Description: Text document