test: fix build of v4l encode demo.

test: fix build of v4l encode demo.

This fixes:
capture.cpp: In function ‘int read_frame()’:
capture.cpp:140:64: error: ‘read’ was not declared in this scope
capture.cpp: In function ‘void init_userp(unsigned int)’:
capture.cpp:431:30: error: ‘getpagesize’ was not declared in this scope
avcenc.cpp:283:26: warning: extended initializer lists only available with -std=c++11 or -std=gnu++11 [enabled by default]
capture.cpp: In function ‘void close_device()’:
capture.cpp:643:24: error: ‘close’ was not declared in this scope

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>