build - Add pkg-config file

Makefile.am

 LIBDIR=@libdir@
 DATADIR=$(PREFIX)/share/espeak-data
 
+pkgconfigdir = $(libdir)/pkgconfig
+pkgconfig_DATA = espeak-ng.pc
+
 SHARED_VERSION=2:48:1 # = *.so.1.1.48
 
 MKDIR=mkdir -p

configure.ac

 dnl Generate output.
 dnl ================================================================
 
-AC_CONFIG_FILES([Makefile])
+AC_CONFIG_FILES([Makefile espeak-ng.pc])
 AC_OUTPUT
 
 AC_MSG_NOTICE([

espeak-ng.pc.in

+prefix=@prefix@
+exec_prefix=@prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: @PACKAGE_NAME@
+Description: @PACKAGE_NAME@ is a multi-lingual software speech synthesizer
+Version: @VERSION@
+Requires:
+Libs: -L${libdir} -lespeak-ng
+Cflags: -I${includedir}