Add include/gpxe as a directory to scan.

Exclude proto/uip, since uip.c and uip_arp.c both have global variables
called "c", which screws up doxygen's auto-generation of links to file
documentation when it encounters a file name such as "hello.c".

src/doxygen.cfg

 
 INPUT                  = @SRCDIRS@ \
                          include \
+                         include/gpxe \
                          arch/@ARCH@/include \
                          doc
 
 # excluded from the INPUT source files. This way you can easily exclude a 
 # subdirectory from a directory tree whose root is specified with the INPUT tag.
 
-EXCLUDE                = 
+EXCLUDE                = proto/uip
 
 # The EXCLUDE_SYMLINKS tag can be used select whether or not files or 
 # directories that are symbolic links (a Unix filesystem feature) are excluded