Update src to matio ver 1.5.1

The *.c and *.h files have been updated from src folder in the
following commit:
(git://matio.git.sourceforge.net/gitroot/matio/matio)
tag: v1.5.1
commit 4f556c6f65a91566b5534995282a285937133d87

New files:
.gitignore
src/mat73.c
src/mat73.h
Updated documentation.

Updated reference to matio manual to version 1.5.1.
Added GPL header to doc files.
Version bump to 0.0.2