loadlibrary() problem in 64-bit Matlab

Hello-

I am trying to load a C++ API into Matlab using loadlibrary() but it is only working in 32-bit Matlab (R2014a). The attached bb_api.zip file contains the bb_api.h header file and has both a 32-bit and 64-bit bb_api.dll in their respective folder. To run it, I copy the correct .dll into the folder with bb_api.h and call

loadlibrary('bb_api','bb_api.h')

While this works for the 32-bit version, when I use the 64-bit .dll in 64-bit Matlab, I get the following error:

Error using loadlibrary (line 422)
Building bb_api_thunk_pcwin64 failed.  Compiler output is:
cl -I"C:\Program Files\MATLAB\R2014a\extern\include"  /W3  /nologo  /D_CRT_SECURE_NO_DEPRECATE
/D_SCL_SECURE_NO_DEPRECATE /D_SECURE_SCL=0   -I"C:\Program Files\MATLAB\R2014a\extern\include" -I"C:\Program
Files\MATLAB\R2014a\simulink\include" -I"C:\Users\mimhof\Documents\GitHub\SDR\Matlab"
-I"C:\Users\mimhof\Documents\GitHub\SDR\Matlab" "bb_api_thunk_pcwin64.c" -LD -Fe"bb_api_thunk_pcwin64.dll"
bb_api_thunk_pcwin64.c
C:\Users\mimhof\Documents\GitHub\SDR\Matlab\bb_api.h(202) : error C2061: syntax error : identifier 'bbOpenDevice'
C:\Users\mimhof\Documents\GitHub\SDR\Matlab\bb_api.h(202) : error C2059: syntax error : ';'
C:\Users\mimhof\Documents\GitHub\SDR\Matlab\bb_api.h(202) : error C2059: syntax error : 'type'
C:\Users\mimhof\Documents\GitHub\SDR\Matlab\bb_api.h(203) : error C2061: syntax error : identifier
'bbCloseDevice'
C:\Users\mimhof\Documents\GitHub\SDR\Matlab\bb_api.h(203) : error C2059: syntax error : ';'
C:\Users\mimhof\Documents\GitHub\SDR\Matlab\bb_api.h(203) : error C2059: syntax error : 'type'

and so on for all the methods available in the API. What would cause this error to occur in 64-bit and not 32-bit?

Thanks!