[Symbol] Search symbols with name and type in a symbol file

Summary:
This patch adds possibility of searching a public symbol with name and type in
a symbol file, not only in a symtab. It is helpful when working with PE, because
PE's symtabs contain only imported / exported symbols only. Such a search is
required for e.g. evaluation of an expression that calls some function of
the debuggee.

Reviewers: zturner, asmith, labath, clayborg, espindola

Reviewed By: clayborg

Subscribers: davide, emaste, arichardson, aleksandr.urakov, jingham,
             lldb-commits, stella.stamenova

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D53368

llvm-svn: 347960