pgsql: Move "#define inline __inline" from port/win32.h to c.h because

Log Message:
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Move "#define inline __inline" from port/win32.h to c.h because Win32
interface builds like libpq need it.

Backpatch addition to 8.1.X.

Tags:
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REL8_1_STABLE

Modified Files:
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pgsql/src/include:
c.h (r1.190.2.2 -> r1.190.2.3)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/c.h.diff?r1=1.190.2.2&r2=1.190.2.3)