VHDL code does not synthesize

VHDL code does not synthesize

References

Reference NO 1

http://stackoverflow.com/questions/15197491/vhdl-code-does-not-synthesize

Reference NO 2

http://academic.csuohio.edu/chu_p/rtl/chu_rtL_book/silde/chap06_1.pdf

Reference NO 3

http://www.mrc.uidaho.edu/mrc/people/jff/vhdl_info/Synthesis_Art_2P.pdf

Reference NO 4

http://www.altium.com/files/learningguides/tr0115%20vhdl%20synthesis%20reference.pdf

Reference NO 5

http://web02.gonzaga.edu/faculty/talarico/cpen430/documents/vhdl-for-synthesis.pdf

Reference NO 6

http://www.vhdl.org/vlog-synth/Mills_Final.pdf

Reference NO 7

http://www.ece.unm.edu/~jimp/vhdl_fpgas/slides/VHDL_synthesis.pdf

Reference NO 8

http://wwwdsa.uqac.ca/~daudet/Cours/Vlsi/DOCUMENTS/repertoire435/Livre-MJS-Smith/Book/CH12/CH12.6.htm