PDB support of function-level linking and splitted functions

Summary:
The patch adds support of splitted functions (when MSVC is used with PGO) and function-level linking feature.

SymbolFilePDB::ParseCompileUnitLineTable function relies on fact that ranges of compiled source files in the binary are continuous and don't intersect each other. The function creates LineSequence for each file and inserts it into LineTable, and implementation of last one relies on continuity of the sequence. But it's not always true when function-level linking enabled, e.g. in added input test file test-pdb-function-level-linking.exe there is xstring's std__basic_string_char_std__char_traits_char__std__allocator_char_____max_size (.00454820) between test-pdb-function-level-linking.cpp's foo (.00454770) and main (.004548F0).

To fix the problem this patch renews the sequence on each address gap.

Reviewers: asmith, zturner

Reviewed By: asmith

Subscribers: aleksandr.urakov, labath, mgorny, lldb-commits

Differential Revision: https://reviews.llvm.org/D47708

llvm-svn: 334260