Fix the Makefile in an attempt to allow installation under opam/Cygwin.

CHANGES

+2015/10/26:
+Fix the Makefile in an attempt to allow installation under opam/Cygwin.
+
 2015/10/23:
 New declaration "%on_error_reduce foo", where foo is a nonterminal symbol.
 This modifies the automaton as follows. In every state where a production of

Makefile

@@ -31,30 +31,40 @@ ifndef USE_OCAMLFIND
   USE_OCAMLFIND = ocamlfind ocamlc -v >/dev/null 2>&1
 endif
 
+# ----------------------------------------------------------------------------
+# Installation paths.
+
+bindir          := ${PREFIX}/bin
+docdir		:= ${PREFIX}/share/doc/menhir
+libdir	        := ${PREFIX}/share/menhir
+mandir          := ${PREFIX}/share/man/man1
+MANS            := menhir.1
+DOCS            := manual.pdf demos
+MLYLIB          := src/standard.mly
+
 # ----------------------------------------------------------------------------
 
 # A few settings differ on Windows versus Unix.
 
+# If the compiler is MSVC, then the name of the executable file ends in .exe,
+# and object file names end in .obj instead of .o.
+
 ifeq "$(shell ocamlc -config | grep ccomp_type)" "ccomp_type: msvc"
-MENHIREXE    := menhir.exe
-OBJ          := obj
+  MENHIREXE    := menhir.exe
+  OBJ          := obj
 # LIBSUFFIX    := lib
 else
-MENHIREXE    := menhir
-OBJ          := o
+  MENHIREXE    := menhir
+  OBJ          := o
 # LIBSUFFIX    := a
 endif
 
-# ----------------------------------------------------------------------------
-# Installation paths.
+# If Cygwin is present, then the path ${libdir} that is recorded in
+# src/installation.ml (see below) must be translated using cygpath.
 
-bindir          := ${PREFIX}/bin
-docdir		:= ${PREFIX}/share/doc/menhir
-libdir	        := ${PREFIX}/share/menhir
-mandir          := ${PREFIX}/share/man/man1
-MANS            := menhir.1
-DOCS            := manual.pdf demos
-MLYLIB          := src/standard.mly
+libdir	        := $(shell if which cygpath >/dev/null ; \
+	             then echo "cygpath -m ${libdir}" ; \
+                     else echo ${libdir} ; fi)
 
 # -------------------------------------------------------------------------