Added support for compiling on MinGW platform

[claudix]

Added rules to compile on MinGW platforms (Microsoft Windows environments):

• Use 'gcc' as compiler.
• Generate DLL file when compiling the library.
• Disable -fPIC when compiling the library (on MinGW platforms all code is already position independent and setting this flag issues an error).

[indutny]

Sorry for a long delay.

@jasnell @mscdex any of you guys have an access to Windows to give it a try? Thanks!

[wildart]

@claudix Can this PR include cygwin platform as well?

I made the following patch

@@ -18,18 +18,30 @@
 # FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 # IN THE SOFTWARE.

+VERSION = 2.7.0
 PLATFORM ?= $(shell sh -c 'uname -s | tr "[A-Z]" "[a-z]"')
+ifeq ($(findstring cygwin,$(PLATFORM)), cygwin)
+PLATFORM = cygwin
+endif
+ifeq ($(findstring mingw,$(PLATFORM)), mingw)
+PLATFORM = mingw
+endif
+
 HELPER ?=
 BINEXT ?=
 ifeq (darwin,$(PLATFORM))
-SONAME ?= libhttp_parser.2.7.0.dylib
+SONAME ?= libhttp_parser.$(VERSION).dylib
 SOEXT ?= dylib
 else ifeq (wine,$(PLATFORM))
 CC = winegcc
 BINEXT = .exe.so
 HELPER = wine
+else ifneq (,$(filter $(PLATFORM),mingw cygwin))
+CC = gcc
+SONAME ?= libhttp_parser.$(VERSION).dll
+SOEXT  ?= dll
 else
-SONAME ?= libhttp_parser.so.2.7.0
+SONAME ?= libhttp_parser.so.$(VERSION)
 SOEXT ?= so
 endif

@@ -50,7 +62,12 @@
 CFLAGS_DEBUG = $(CFLAGS) -O0 -g $(CFLAGS_DEBUG_EXTRA)
 CFLAGS_FAST = $(CFLAGS) -O3 $(CFLAGS_FAST_EXTRA)
 CFLAGS_BENCH = $(CFLAGS_FAST) -Wno-unused-parameter
+
+ifneq (,$(filter $(PLATFORM),mingw cygwin))
+CFLAGS_LIB = $(CFLAGS_FAST)
+else
 CFLAGS_LIB = $(CFLAGS_FAST) -fPIC
+endif

 LDFLAGS_LIB = $(LDFLAGS) -shared

@@ -141,7 +158,7 @@
    rm -f *.o *.a tags test test_fast test_g \
        http_parser.tar libhttp_parser.so.* \
        url_parser url_parser_g parsertrace parsertrace_g \
-       *.exe *.exe.so
+       *.exe *.exe.so *.dll

 contrib/url_parser.c:  http_parser.h
 contrib/parsertrace.c: http_parser.h

and tested it on CYGWIN_NT-6.1 8308-HSQ0KM1 2.5.2(0.297/5/3) 2016-06-23 14:27 i686 Cygwin

[claudix]

@wildart I'd like to. However I recommend you opening your own PR because, as you can notice, my PR has been waiting for 4 months and is still waiting to be merged.... No hope to finally see it merged. BTW, good idea to create the VERSION variable... Repeating the version string throughout the file is error prone and time wasting!

[wildart]

It would be nice to include windows related changes into this patch: #321.

BTW, hardcoding gcc compiler is not a good idea. what is wrong with CC variable?