Fix FTBFS with stricter C++11.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>
(cherry picked from commit a178ab7c22)

src/makefrontend.cpp

@@ -33,10 +33,10 @@
 #define PATH_ELEM "[a-zA-Z0-9_\\.\\-]+"
 
 #define RE_FILE_LINE \
-	"((?:\\/)?(?:"PATH_ELEM"\\/)*"PATH_ELEM"):([0-9]+)(:[0-9]+)?: (.*)"
+	"((?:\\/)?(?:" PATH_ELEM "\\/)*" PATH_ELEM "):([0-9]+)(:[0-9]+)?: (.*)"
 #define RE_ENTER_DIR \
 	"Entering directory " \
-	"\\`((\\/)?("PATH_ELEM"\\/)*"PATH_ELEM")"
+	"\\`((\\/)?(" PATH_ELEM "\\/)*" PATH_ELEM ")"
 #define RE_EXIT_DIR "Leaving directory"
 
 /**