Add chaz_MakeFile_add_compiled_exe

Used to compile and link an executable.
Add chaz_CC_shared_lib_file

Returns the filename of a shared library.
Better error messages in Charmonizer::Core::CFlags
Add code coverage target to Makefile

Create HTML pages with coverage data using lcov like this:

$ ./configure --enable-coverage
$ make
$ make coverage
Compile and link lemon in one go

This way we have better control over the compiler flags used.
Regenerate charmonizer.c
Update installation instructions for C library