Add /usr/local/include and /usr/local/lib to CPPFLAGS and LDFLAGS

This allows to avoid extra options for BSDs and strangle Linux systems, where
some libraries may be installed under "/usr/local" prefix.

configure

@@ -3171,6 +3171,10 @@ ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $
 ac_compiler_gnu=$ac_cv_c_compiler_gnu
 
 
+# BSD locations for headers and libraries from packages, Linux locations for self-compiled stuff.
+CPPFLAGS="$CPPFLAGS -I/usr/local/include"
+LDFLAGS="$LDFLAGS -L/usr/local/lib"
+
 # Checks for libraries.
 
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sqrt in -lm" >&5

configure.ac

@@ -8,6 +8,10 @@ m4_include([ax_lua.m4])
 # Checks for programs.
 AC_PROG_CC
 
+# BSD locations for headers and libraries from packages, Linux locations for self-compiled stuff.
+CPPFLAGS="$CPPFLAGS -I/usr/local/include"
+LDFLAGS="$LDFLAGS -L/usr/local/lib"
+
 # Checks for libraries.
 AC_CHECK_LIB([m], [sqrt])
 AC_SEARCH_LIBS([clock_gettime], [rt])