Fix for FreeImage.h typedef problems for OSX/iOS Xcode

Fix for FreeImage error when compiling on OSX for iOS (Xcode)

Problem:
"error: typedef redefinition with different types ('signed char' vs
'int32_t' (aka 'int'))
typedef signed char BOOL; "

Solution:
Use #define and #undef instead of typedef for the type definitions.

Updated for the new version of FreeType and to support the new 64bit data structures with the define/undef.
Based on the changes @ofTheo made 3 years ago to the same file
https://github.com/openframeworks/openFrameworks/issues/76