~fboucault/paf/documentation_fixes

Merge with api-fixing.
Added const and G_GNUC_NULL_TERMINATED where needed.
Renamed "source" and "progression" to "fraction".

added added

removed removed

gboolean (*remove_modifier) (PafTransformation *transformation,

PafModifier *modifier);

gboolean (*has_modifier) (PafTransformation *transformation,

PafModifier *modifier);

const PafModifier *modifier);

gboolean (*update) (PafTransformation *transformation,

gfloat source);

gfloat fraction);

void (*set_trigger) (PafTransformation *transformation,

PafConditionFunc condition,

gpointer user_data,

gboolean paf_transformation_remove_modifier (PafTransformation *transformation,

PafModifier *modifier);

gboolean paf_transformation_has_modifier (PafTransformation *transformation,

PafModifier *modifier);

const PafModifier *modifier);

gboolean paf_transformation_update (PafTransformation *transformation,

gfloat source);

gfloat fraction);

void paf_transformation_set_trigger (PafTransformation *transformation,

PafConditionFunc *condition,