Build on GNU/kfreeBSD and GNU/Hurd

Use __GLIBC__ instead of __linux
Simplify Make.inc as per JuliaMath/openspecfun@e91925a

Make.inc

@@ -82,37 +82,22 @@ override OS=WINNT
 endif
 
 #keep these if statements separate
-ifeq ($(OS), WINNT)
-SHLIB_EXT = dll
-SONAME_FLAG = -soname
-CFLAGS_add += -nodefaultlibs
-shlibdir = $(bindir)
-else
-shlibdir = $(libdir)
-endif
-
-ifeq ($(OS), Linux)
-SHLIB_EXT = so
-SONAME_FLAG = -soname
-CFLAGS_add+=-fPIC
-endif
-
-ifeq ($(OS), FreeBSD)
-SHLIB_EXT = so
-SONAME_FLAG = -soname
-CFLAGS_add+=-fPIC
-endif
-
-ifeq ($(OS), OpenBSD)
-SHLIB_EXT = so
-SONAME_FLAG = -soname
-CFLAGS_add+=-fPIC
-endif
 
-ifeq ($(OS), Darwin)
-SHLIB_EXT = dylib
-SONAME_FLAG = -install_name
-CFLAGS_add+=-fPIC
+ifeq ($(OS), WINNT)
+  SHLIB_EXT = dll
+  SONAME_FLAG = -soname
+  override CFLAGS_add += -nodefaultlibs
+  shlibdir = $(bindir)
+ else
+  ifeq ($(OS), Darwin)
+    SHLIB_EXT = dylib
+    SONAME_FLAG = -install_name
+  else
+    SHLIB_EXT = so
+    SONAME_FLAG = -soname
+  endif
+  override CFLAGS_add += -fPIC
+  shlibdir = $(libdir)
 endif
 
 # The target specific FLAGS_add

i387/bsd_asm.h

@@ -39,7 +39,7 @@
 #if defined(__APPLE__)
 #include "osx_asm.h"
 #define CNAME(x) EXT(x)
-#elif defined(__FreeBSD__) || defined(__linux__) || defined(_WIN32)
+#else
 #include "bsd_cdefs.h"
 
 #ifdef PIC

src/fpmath.h

@@ -47,7 +47,7 @@
 #define _PDP_ENDIAN       __ORDER_PDP_ENDIAN__
 #define _BYTE_ORDER       __BYTE_ORDER__
 
-#elif defined(__linux)
+#elif defined(__GLIBC__)
 
 #include <features.h>
 #include <endian.h>

src/types-compat.h

@@ -5,7 +5,7 @@
 #include <limits.h>
 #include <stdint.h>
 
-#ifdef __linux__
+#ifdef __GLIBC__
 /* Not sure what to do about __pure2 on linux */
 #define __pure2 
 #endif