gitignore: ignore files created by msvc

exp files are created in every build and contain export information
of the libraries. Both pdb and ilk are created during debug builds,
and contain linking and debug information used by MSVC.
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

.gitignore

@@ -4,9 +4,12 @@
 *.def
 *.dll
 *.exe
+*.exp
 *.h.c
+*.ilk
 *.lib
 *.pc
+*.pdb
 *.so
 *.so.*
 *.ver