This commit fixes the improper patch in the pull request #7.
When building pforth on the Linux system with glibc version before
2.19, defining _GNU_SOURCE is needed for using ECHOCTL in the
source. However, the later version of glibc uses _DEFAULT_SOURCE
instead of _GNU_SOURCE for the same purpose, we will need both symbols
for both older glibc and newer glibc.
VPATH = .:$(CSRCDIR):$(CSRCDIR)/posix:$(CSRCDIR)/stdio:$(CSRCDIR)/win32_console:$(CSRCDIR)/win32
XCFLAGS = $(CCOPTS)
-XCPPFLAGS = -DPF_SUPPORT_FP -D_GNU_SOURCE
+XCPPFLAGS = -DPF_SUPPORT_FP -D_DEFAULT_SOURCE -D_GNU_SOURCE
XLDFLAGS = $(WIDTHOPT)
CPPFLAGS = -I. $(XCPPFLAGS)