Clarifies the license applying on the manual and added a docx copy of the manual to the source

readme.txt

@@ -43,6 +43,8 @@ GLM 0.9.4.3: 2013-0X-XX
 - Fixed C++11 mode for GCC, couldn't be enabled without MS extensions
 - Fixed squad, intermediate and exp quaternion functions
 - Fixed GTX_polar_coordinates euclidean function, takes a vec2 instead of a vec3
+- Clarify the license applying on the manual
+- Added a docx copy of the manual
 
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 GLM 0.9.4.2: 2013-02-14