Replace usleep with std::this_thread::sleep_for

[arntanguy]

As reported in issue #207 , with some version of Eigen compilation fails with errors regarding usleep not being found.

This can be solved in one of two ways, including the proper header unistd.h, that was removed from Eigen headers, or better yet, using the now standard C++11 std::this_thread::sleep_for.

This commit does the latter for all uses of usleep.
A similar change was also proposed as part of the more general PR #215 , that intends to fix multiplateform compilation.

[Introvertuous]

+1

[meitiever]

how could i specify compiler C++11 in build.sh?
thanks

[arntanguy]

@meitiever This is already specified in the CMakeList

include(CheckCXXCompilerFlag)
CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
CHECK_CXX_COMPILER_FLAG("-std=c++0x" COMPILER_SUPPORTS_CXX0X)
if(COMPILER_SUPPORTS_CXX11)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
   add_definitions(-DCOMPILEDWITHC11)
   message(STATUS "Using flag -std=c++11.")
elseif(COMPILER_SUPPORTS_CXX0X)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")
   add_definitions(-DCOMPILEDWITHC0X)
   message(STATUS "Using flag -std=c++0x.")
else()
   message(FATAL_ERROR "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.")
endif()

[facontidavide]

+1 for this PR

[aravindev]

These changes do work.

[GSORF]

Please merge this PR.

thank you.