Move header to modp_b64 subdir.

libchromeos imports modp_b64 via modp_b64/modp_b64.h. Moving it into a
subdirectory make the import cleaner.

(cherry-pick from b1e6e2024f4b05e9747556c0937d6770da74ba13)

Change-Id: Ib4b778bd103af1f75ea7ba5333e722a7699f91e7
diff --git a/Android.mk b/Android.mk
index cfe35cb..99bce20 100644
--- a/Android.mk
+++ b/Android.mk
@@ -19,6 +19,7 @@
 LOCAL_SRC_FILES := modp_b64.cc
 LOCAL_CPP_EXTENSION := .cc
 LOCAL_CFLAGS := -Wall -Werror
+LOCAL_C_INCLUDES := $(LOCAL_PATH)/modp_b64
 LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)
 include $(BUILD_STATIC_LIBRARY)
 
@@ -27,5 +28,6 @@
 LOCAL_SRC_FILES := modp_b64.cc
 LOCAL_CPP_EXTENSION := .cc
 LOCAL_CFLAGS := -Wall -Werror
+LOCAL_C_INCLUDES := $(LOCAL_PATH)/modp_b64
 LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)
 include $(BUILD_HOST_STATIC_LIBRARY)
diff --git a/Makefile b/Makefile
index a093384..c33ff75 100644
--- a/Makefile
+++ b/Makefile
@@ -14,6 +14,7 @@
 
 include common.mk
 
+CXXFLAGS += -I$(SRC)/modp_b64/
 CXX_STATIC_LIBRARY(libmodpb64.pie.a): $(CXX_OBJECTS)
 
 all: CXX_STATIC_LIBRARY(libmodpb64.pie.a)
diff --git a/modp_b64.h b/modp_b64/modp_b64.h
similarity index 100%
rename from modp_b64.h
rename to modp_b64/modp_b64.h