Changes:
1. There may be zero spaces between 'include' and '<...>'.
2. Blanks and '=' may occur inside '<...>' but '>' may not.
3. There must be at least one character inside '<...>'.
References:
Change 1:
C: www.open-std.org/jtc1/sc22/wg14/www/docs/n2310.pdf#subsection.6.10.2
C++: www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4659.pdf#section.19.2
Changes 2 and 3:
C: www.open-std.org/jtc1/sc22/wg14/www/docs/n2310.pdf#subsection.6.4.7
C++: www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/n4659.pdf#section.5.8
Signed-off-by: Hussam al-Homsi <sawuare@gmail.com>