split path-specific ('C:\FOO' instead of '/foo') stuff into MKSH_DOSPATH:

• backslashes as directory separators
• semicolon as $PATH separator
• drive letters are absolute paths

exec.c

@@ -23,7 +23,7 @@
 
 #include "sh.h"
 
-__RCSID("$MirOS: src/bin/mksh/exec.c,v 1.191 2017/03/22 00:20:51 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/exec.c,v 1.192 2017/04/02 13:08:06 tg Exp $");
 
 #ifndef MKSH_DEFAULT_EXECSHELL
 #define MKSH_DEFAULT_EXECSHELL	MKSH_UNIXROOT "/bin/sh"
@@ -1136,7 +1136,7 @@ findcom(const char *name, int flags)
 	union mksh_cchack npath;
 
 	if (mksh_vdirsep(name)
-#ifdef __OS2__
+#ifdef MKSH_DOSPATH
 	    && (strcmp(name, T_builtin) != 0)
 #endif
 	    ) {