Fixed compile errors in VS / gcc for recent commits.

Tested: on Windows & Linux.

Change-Id: I90e18c448fc2fafeb83a6cdc3776174479874562
Fixed compiler warning for int to char conversion.

Change-Id: Idc6c152ebf9e733ac72c01f3888b69e3b5f33aa9
Tested: on Linux.
Made reading read-only ByteBuffers work.

Also added new constructor that allows ByteBuffer reuse.

Change-Id: I9c20ea96c67533066461f4e23b0d03b9b47cd068
Tested: on OS X.
Ignore gtags database
Merge branch 'master' of github.com:apurvam/flatbuffers

Conflicts:
	include/flatbuffers/util.h