Class-specific Extremal Region Filter algorithm as proposed in :
Neumann L., Matas J.: Real-Time Scene Text Localization and Recognition, CVPR 2012.

High-level C++ interface and implementation of algorithm is in the objdetect module.
C++ example, a test image, and the default classifiers in xml files.
add opencv_ml headers to precomp
fixed some warnings on build 4285
fixed compilation errors and warnings on builds 3298 and 4384
using explicit keyword in the ERStat constructor for safe contruction
using Rect for storing the bounding box instead of an integer array
removed extra cv:: scope qualifiers for better readability
removed some unnecessary ERStat members as they are easily computable from others
Merge pull request #1159 from lluisgomez:scene_text_detection_NM