fixed #warning error when compiling under mingw-64.

Fixes the error below when building/compiling against mingw64 under
windows.

#warning Please include winsock2.h before windows.h
Changed makefile for runtime to look for HOST_ARCH environment variable.

Adding this functionality allows one to cross compile to another
architecture other than the current host. To compile to another
architecture than the current host, we can set bash environment variable
via 'export HOST_ARCH=x86_64'. This is needed when compiling for 64 bit
in windows under MSYS - which is a 32 bit process.
Revert "fixed #warning error when compiling under mingw-64."

This reverts commit 551bb0597e7ad35ac27767ffcc7e2290b5f3dec3.
revert back the winsock2.h modification.
Revert "revert back the winsock2.h modification."

This reverts commit 85cb9e054fc8bde954e31ba845c71472f9525d7b.
Added compiler directives to address mingw winsock2.h and windows.h warning.
Revert "Added compiler directives to address mingw winsock2.h and windows.h warning."

This reverts commit 9c02b642b51c7e90aaf2df252b1c097d3d7a7f22.