Fix typo in pcre.m4: corrected PCRE_CFLAGS assignment

Author: Gabor Berkes

build/pcre.m4

@@ -106,7 +106,7 @@ else
         LIBS=$save_LIBS
     fi
 
-    PCRE_CFLAGS="-DWITH_PCRE$ {PCRE_CFLAGS}"
+    PCRE_CFLAGS="-DWITH_PCRE ${PCRE_CFLAGS}"
     AC_SUBST(PCRE_CONFIG)
     AC_SUBST(PCRE_VERSION)
     AC_SUBST(PCRE_CPPFLAGS)