Improvements and sf3 import

[davy7125]

Integration improvement (fix #11):

• preprocessor variable to loose the xml and libsnd dependencies
• namespace SfTools
• smallSf now a class variable
• C++11 not needed anymore (struct initialization)
• dynamic declaration of array now ok with visual C++ (fix #10)
• warning and unused variables removed

Bug fix:

• sample links now kept in the soundfont (fix #9)
• the sm24 chunk doesn't stop the program anymore

New feature:

• The conversion tool can now convert back from sf3 to sf2 (fix #22)

Improvement:

• the attenuation is stored in the ogg file so that we can revert it during the extraction

[hmoffatt]

@davy7125 the code on the your branch doesn't compile. sfconvert.cpp is missing semicolons at lines 121-122, and sf.smallSf does not exist at line 131.

[hmoffatt]

Also, I converted an SF3 of mine back to SF2 and it sounds terrible, nothing like the original SF2 (or SF3).

[Jojo-Schmitz]

Seems a rebase is needed to fix merge conflicts