ISSUE-129: Remove obsolete macros from configure.ac

[dmalec]

Resolves #129

• AC_CONFIG_HEADER - this is an obsolete synonym for AC_CONFIG_HEADERS. https://www.gnu.org/software/automake/manual/1.12/html_node/Obsolete-Macros.html

• AC_HEADER_STDC - this is an obsolete macro, autoconf recommends handling old systems with missing string functions on a case-by-case basis instead of using this macro. https://www.gnu.org/software/autoconf/manual/autoconf-2.67/html_node/Particular-Headers.html

Test Environments

• OSX Catalina (10.15.7) w/ wxWidgets 3.0.5
• Ubuntu Bionic (18.04.5) w/ wxWidgets 3.0.5


[jrincayc]

@dmalec Thank you for fixing this and issue 126 :)

[dmalec]

@jrincayc you're welcome, no worries :)

[pmetzger]

Thank you!