include: make header guards more sane The C++ standard[1] says: Each identifier that contains a double underscore __ or begins with an underscore followed by an uppercase letter is reserved to the implementation for any use. [1]: https://timsong-cpp.github.io/cppwp/n4659/lex.name#3.1

lib_LTLIBRARIES = libpugixml.la

libpugixml_la_SOURCES = \
	src/pugixml.cpp \
	src/pugiconfig.hpp

include_HEADERS = src/pugixml.hpp

libpugixml_la_CXXFLAGS = -std=c++11
ACLOCAL_AMFLAGS = -I m4