When -mean is selected, currently pprof divides the sample value
by value[0], which is expected to be the number of samples. This
is intended to produce mean value per sample. These means cannot
be added. Instead, we should add the value and the number of samples
independently and perform the division at the end.

To do this we will create a separate function to get the number of samples,
and accumulate it independently from the sample value (weigth) and apply
the division after the accumulation is completed.

When generating callgrind format output, produce cost lines at
instruction granularity. This allows visualizers supporting the
callgrind format to display instruction-level profiling information.

We also need to provide the object file (ob=) in order for tools to find
the object file to disassemble when displaying assembly.

We opportunistically group cost lines corressponding to the same
function together, reducing the number of superfluous description lines.
Subposition compression (relative position numbering) is also used to
reduce the output size.

This will allow merging nodes for multiple instantiations of
C++ templates. A graph option is introduced to preserve older
behavior.

When using the call_tree option and generating a graph for kcachegrind,
it will merge back nodes that are distinct on the tree, producing some
confusing results. Add a suffix so that these entries are kept separate.

This addresses the problem described in
http://yosefk.com/blog/how-profilers-lie-the-cases-of-gprof-and-kcachegrind.html ,
particularly the summary "Choosing a profiler is hard" section.

This is to keep the new TrimTree functionality from breaking any code
currently using the public interface. We do this by separating NodeSet
from nodePtrSet and creating different functions for each.

If we are deleting a node N, if the edge between N and its parent and
the edge between N and its child are both inline, then the resulting
residual edge from N's parent and the child will also be inline.

In a graph, NodeInfo maps one to one to the nodes, so it suffices to
just find the top NodeInfo s and only keep those nodes in the graph. In
a tree however, a single NodeInfo may map to many nodes. As of this
commit, a call to 'web 10' in pprof on a tree will return all the nodes
corresponding with the top 10 NodeInfo s.

Weblist provides source and assembly combined in a web document.
It needs access to the binary to print the assembly, but currently
refuses to generate the source if the binary can't be find.

Fall back to just generating the source if the binary isn't found.

Graphs are built using Go maps which do not provide a determinist
traversal. We sort the nodes to remove the non-determinism, but
the sort fails to provide a fully deterministic ordering in cases
where the attributes being sorted have equal values. Detect those
cases and fallback to a full comparison of all fields.

This reverts commit 9c191ebbce.
The trimproto option is no longer needed, removing it to avoid code growth.

When generating a call tree, pprof was using a map to keep track of all the
inline nodes for a location. That is incorrect as it may cause inline functions
at different nesting levels to reuse the same node, causing the resulting graph
to not be a tree.

When creating a tree nodes with the same info may appear on multiple places
in the tree. Keeping one of them preserves them all, which may cause disconnected
nodes to remain. To ensure the resulting graph is a connected tree, do not include
children on any removed node, which is suitable for the normal tree refinement
(nodecount and nodefraction) but does not allow visual refinement, which may eliminate
intermediate nodes. Disable visual mode refinement for call_tree to avoid this issue.

Add new trimproto option that generates a new profile while removing
symbol information for functions below nodefraction. This reduces the
profile sizes significantly.

Separate implementation of graph and tree creation to speed it up.
Graph implementation maps upfront all locations to sequences of nodes,
tree implementation uses a per-parent map to keep track of a different
node per location per parent.

Non functional changes -- pre-size maps and slices to reduce
cost of building a graph out of a profile.

When reconciling samples, cleanup file paths to allow functions to be
combined if their source filenames match after cleanup (eg "src.cpp" and
"./src.cpp").

Also clean up existing uses of filepath to avoid passing empty strings
to it: filepath.Base("") returns "."

Also update the build instructions to use go get