sanitise sign comparisons

This is a mechanical change addressing the various sign comparison warnings that
are identified by both clang and gcc.  This helps cleanup some of the warning
spew that occurs during builds.

llvm-svn: 205390
diff --git a/lldb/source/Symbol/ObjectFile.cpp b/lldb/source/Symbol/ObjectFile.cpp
index 9314335..c3294c9 100644
--- a/lldb/source/Symbol/ObjectFile.cpp
+++ b/lldb/source/Symbol/ObjectFile.cpp
@@ -486,7 +486,7 @@
     else
     {
         const uint64_t section_file_size = section->GetFileSize();
-        if (section_offset < section_file_size)
+        if (section_offset < static_cast<off_t>(section_file_size))
         {
             const uint64_t section_bytes_left = section_file_size - section_offset;
             uint64_t section_dst_len = dst_len;