autotools: use the variables from autotools for the install locations.

Makefile.am

-PREFIX=/usr
-BINDIR=$(PREFIX)/bin
-INCDIR=$(PREFIX)/include/espeak
-LIBDIR=$(PREFIX)/lib
+PREFIX=@prefix@
+BINDIR=@bindir@
+INCDIR=@includedir@/espeak
+LIBDIR=@libdir@
 DATADIR=$(PREFIX)/share/espeak-data
 
 PLATFORM=big_endian
 	cp $< $@
 
 src/libespeak.a: $(common_SOURCE) $(libespeak_SOURCE)
-	cd src && make libespeak.a PREFIX=$(PREFIX) && cd ..
+	cd src && make libespeak.a && cd ..
 
 src/libespeak.so: $(common_SOURCE) $(libespeak_SOURCE)
-	cd src && make libespeak.so PREFIX=$(PREFIX) && cd ..
+	cd src && make libespeak.so && cd ..
 
 src/speak: $(common_SOURCE) src/speak.cpp
-	cd src && make speak PREFIX=$(PREFIX) && cd ..
+	cd src && make speak && cd ..
 
 src/espeak: src/libespeak.so src/espeak.cpp
-	cd src && make espeak PREFIX=$(PREFIX) && cd ..
+	cd src && make espeak && cd ..
 
 src/espeakedit: $(common_SOURCE) $(libespeak_SOURCE) $(espeakedit_SOURCE)
-	cd src && make espeakedit PREFIX=$(PREFIX) && cd ..
+	cd src && make espeakedit && cd ..
 
 espeak-phoneme-data:
 	cd platforms/$(PLATFORM) && make PREFIX=$(PREFIX) && cd ../..

src/Makefile.am

-# remove -fno-exceptions  if it causes problems with stdio library on some platforms (ARM)
-
-DATADIR=/usr/share/espeak-data
+PREFIX=@prefix@
+BINDIR=@bindir@
+INCDIR=@includedir@/espeak
+LIBDIR=@libdir@
+DATADIR=${PREFIX}/share/espeak-data
 
-PREFIX=/usr
-BINDIR=$(PREFIX)/bin
-INCDIR=$(PREFIX)/include/espeak
-LIBDIR=$(PREFIX)/lib
+# remove -fno-exceptions  if it causes problems with stdio library on some platforms (ARM)
 
 RELEASE = 1.46
 SPEAK = speak