add lua.hpp to install_header

It looks as though 5.2 accidentally dropped the included lua.hpp file from install_header. 5.1.5 still has it. This file is required for C++ projects using Lua.
fix error and mem leak found by cppcheck
allow for optional static compilation by overriding BUILD_SHARED_LIBS to OFF
Merge pull request #6 from biometrics/master

Allow for optional static compilation by overriding BUILD_SHARED_LIBS to OFF
Merge pull request #4 from dekimsey/patch-1

add lua.hpp to install_header
Merge pull request #5 from greg-a/master

fix error and mem leak found by cppcheck
Update to version 5.2.3
Loadlib fix for newer Cygwin releases
Correction of path format
merge upstream

Signed-off-by: bigcat <rc.local@qq.com>