Improvements:

• drop glm__memcpy, glm__memset and glm__memzero
  • copy matrix items manually in _ucopy functions
• update docs

New Functions:

• float glm_mat3_rmc(vec3 r, mat3 m, vec3 c) multiplies row vector, matrix and column vector and returns scalar.
• glm_mat3_zero(mat3 mat) , glm_mat4_zero(mat4 mat) make given matrix zero.