Adding source code to RetrieveSymbols for PE/PDB retrieval.

tools/win/RetrieveSymbols/ReadMe.txt

+This tool is designed to download PE files and symbols from symbol servers.
+Normally this is done automatically by tools such as windbg but it can be
+helpful to be able to download these files on demand.
+
+Sample usage:
+
+> rem Add the VS tools to the path, for access to dumpbin
+> "%vs120comntools%vsvars32.bat"
+
+D:\src\chromium\src\tools\win>dumpbin /headers "c:\Program Files (x86)\Google\Chrome\Application\chrome.exe" | findstr "RSDS date image"
+        54E3AECF time date stamp Tue Feb 17 13:12:47 2015
+          400000 image base (00400000 to 004D2FFF)
+            0.00 image version
+           D3000 size of image
+    54E3AECF cv           5D 0008DF80    8D380    Format: RSDS, {283A66AE-3EF3-4383-8798-F6617112B1F6}, 1, C:\b\build\slave\win\build\src\out\Release\initialexe\chrome.exe.pdb
+
+> RetrieveSymbols {283A66AE-3EF3-4383-8798-F6617112B1F6}, 1 chrome.exe.pdb
+Parsing symbol data for a PDB file.
+Looking for 283A66AE3EF343838798F6617112B1F6 1 chrome.exe.pdb.
+Found symbol file - placed it in d:\src\symbols\chrome.exe.pdb\283A66AE3EF343838798F6617112B1F61\chrome.exe.pdb.
+
+> RetrieveSymbols 54E3AECF D3000 chrome.exe
+Parsing symbol data for a PE (.dll or .exe) file.
+Looking for chrome.exe 54e3aecf d3000.
+Found symbol file - placed it in d:\src\symbols\chrome.exe\54E3AECFd3000\chrome.exe.
+
+The first invocation of RetrieveSymbols uses the GUID, age, and PDB name from
+the RSDS line of the dumpbin output -- the extraneous '{', '}', ',' and '-'
+characters are stripped out.
+
+The second invocation of RetrieveSymbols uses the time date stamp from the
+first line of the dumpbin output, the "size of image" data, and the
+executable name.
+
+This information can also be obtained from breakpad reports, from windbg
+by using "lmv m chrome_elf" and "!lmi chrome_elf.dll", from ETW traces,
+and from other sources.