Accept colon separated paths with -L and -I

This allows passing colon separated paths to
  tcc_add_library_path
  tcc_add_sysinclude_path
  tcc_add_include_path

Also there are new configure variables
  CONFIG_TCC_LIBPATH
  CONFIG_TCC_SYSINCLUDE_PATHS
which define the lib/sysinclude paths all in one and can
be overridden from configure/make

For TCC_TARGET_PE semicolons (;) are used as separators

Also, \b in the path string is replaced by s->tcc_lib_path
(CONFIG_TCCDIR rsp. -B option)

tccgen.c

@@ -90,6 +90,15 @@ ST_INLN int is_float(int t)
     return bt == VT_LDOUBLE || bt == VT_DOUBLE || bt == VT_FLOAT;
 }
 
+/* we use our own 'finite' function to avoid potential problems with
+   non standard math libs */
+/* XXX: endianness dependent */
+ST_FUNC int ieee_finite(double d)
+{
+    int *p = (int *)&d;
+    return ((unsigned)((p[1] | 0x800fffff) + 1)) >> 31;
+}
+
 ST_FUNC void test_lvalue(void)
 {
     if (!(vtop->r & VT_LVAL))